diff --git a/broker/broker.go b/broker/broker.go
index 369a5352..53b15d4e 100644
--- a/broker/broker.go
+++ b/broker/broker.go
@@ -20,6 +20,8 @@ var (
 	ErrDisconnected = errors.New("broker disconnected")
 	// ErrInvalidMessage returns when invalid Message passed
 	ErrInvalidMessage = errors.New("invalid message")
+	// ErrInvalidHandler returns when subscriber passed to Subscribe
+	ErrInvalidHandler = errors.New("invalid handler")
 	// DefaultGracefulTimeout
 	DefaultGracefulTimeout = 5 * time.Second
 )
@@ -87,9 +89,3 @@ type Subscriber interface {
 	// Unsubscribe from topic
 	Unsubscribe(ctx context.Context) error
 }
-
-// MessageHandler func signature for single message processing
-type MessageHandler func(Message) error
-
-// MessagesHandler func signature for batch message processing
-type MessagesHandler func([]Message) error
diff --git a/broker/memory/memory.go b/broker/memory/memory.go
index 1ca50e87..86430a4c 100644
--- a/broker/memory/memory.go
+++ b/broker/memory/memory.go
@@ -2,6 +2,7 @@ package broker
 
 import (
 	"context"
+	"strings"
 	"sync"
 
 	"go.unistack.org/micro/v4/broker"
@@ -34,6 +35,30 @@ type memoryMessage struct {
 	opts  broker.PublishOptions
 }
 
+func (m *memoryMessage) Ack() error {
+	return nil
+}
+
+func (m *memoryMessage) Body() []byte {
+	return m.body
+}
+
+func (m *memoryMessage) Header() metadata.Metadata {
+	return m.hdr
+}
+
+func (m *memoryMessage) Context() context.Context {
+	return m.ctx
+}
+
+func (m *memoryMessage) Topic() string {
+	return ""
+}
+
+func (m *memoryMessage) Unmarshal(dst interface{}, opts ...codec.Option) error {
+	return m.c.Unmarshal(m.body, dst)
+}
+
 type Subscriber struct {
 	ctx     context.Context
 	exit    chan bool
@@ -43,25 +68,38 @@ type Subscriber struct {
 	opts    broker.SubscribeOptions
 }
 
-func (m *Broker) Options() broker.Options {
-	return m.opts
+func (b *Broker) newCodec(ct string) (codec.Codec, error) {
+	if idx := strings.IndexRune(ct, ';'); idx >= 0 {
+		ct = ct[:idx]
+	}
+	b.RLock()
+	c, ok := b.opts.Codecs[ct]
+	b.RUnlock()
+	if ok {
+		return c, nil
+	}
+	return nil, codec.ErrUnknownContentType
 }
 
-func (m *Broker) Address() string {
-	return m.addr
+func (b *Broker) Options() broker.Options {
+	return b.opts
 }
 
-func (m *Broker) Connect(ctx context.Context) error {
+func (b *Broker) Address() string {
+	return b.addr
+}
+
+func (b *Broker) Connect(ctx context.Context) error {
 	select {
 	case <-ctx.Done():
 		return ctx.Err()
 	default:
 	}
 
-	m.Lock()
-	defer m.Unlock()
+	b.Lock()
+	defer b.Unlock()
 
-	if m.connected {
+	if b.connected {
 		return nil
 	}
 
@@ -75,65 +113,79 @@ func (m *Broker) Connect(ctx context.Context) error {
 	// set addr with port
 	addr = mnet.HostPort(addr, 10000+i)
 
-	m.addr = addr
-	m.connected = true
+	b.addr = addr
+	b.connected = true
 
 	return nil
 }
 
-func (m *Broker) Disconnect(ctx context.Context) error {
+func (b *Broker) Disconnect(ctx context.Context) error {
 	select {
 	case <-ctx.Done():
 		return ctx.Err()
 	default:
 	}
 
-	m.Lock()
-	defer m.Unlock()
+	b.Lock()
+	defer b.Unlock()
 
-	if !m.connected {
+	if !b.connected {
 		return nil
 	}
 
-	m.connected = false
+	b.connected = false
 	return nil
 }
 
-func (m *Broker) Init(opts ...broker.Option) error {
+func (b *Broker) Init(opts ...broker.Option) error {
 	for _, o := range opts {
-		o(&m.opts)
+		o(&b.opts)
 	}
 
-	m.funcPublish = m.fnPublish
-	m.funcSubscribe = m.fnSubscribe
+	b.funcPublish = b.fnPublish
+	b.funcSubscribe = b.fnSubscribe
 
-	m.opts.Hooks.EachPrev(func(hook options.Hook) {
+	b.opts.Hooks.EachPrev(func(hook options.Hook) {
 		switch h := hook.(type) {
 		case broker.HookPublish:
-			m.funcPublish = h(m.funcPublish)
+			b.funcPublish = h(b.funcPublish)
 		case broker.HookSubscribe:
-			m.funcSubscribe = h(m.funcSubscribe)
+			b.funcSubscribe = h(b.funcSubscribe)
 		}
 	})
 
 	return nil
 }
 
-func (m *Broker) Publish(ctx context.Context, topic string, messages ...broker.Message) error {
-	return m.funcPublish(ctx, topic, messages...)
+func (b *Broker) NewMessage(ctx context.Context, hdr metadata.Metadata, body interface{}, opts ...broker.PublishOption) (broker.Message, error) {
+	options := broker.NewPublishOptions(opts...)
+	m := &memoryMessage{ctx: ctx, hdr: hdr, opts: options}
+	c, err := b.newCodec(m.opts.ContentType)
+	if err == nil {
+		m.body, err = c.Marshal(body)
+	}
+	if err != nil {
+		return nil, err
+	}
+
+	return m, nil
 }
 
-func (m *Broker) fnPublish(ctx context.Context, topic string, messages ...broker.Message) error {
-	return m.publish(ctx, topic, messages...)
+func (b *Broker) Publish(ctx context.Context, topic string, messages ...broker.Message) error {
+	return b.funcPublish(ctx, topic, messages...)
 }
 
-func (m *Broker) publish(ctx context.Context, topic string, messages ...broker.Message) error {
-	m.RLock()
-	if !m.connected {
-		m.RUnlock()
+func (b *Broker) fnPublish(ctx context.Context, topic string, messages ...broker.Message) error {
+	return b.publish(ctx, topic, messages...)
+}
+
+func (b *Broker) publish(ctx context.Context, topic string, messages ...broker.Message) error {
+	b.RLock()
+	if !b.connected {
+		b.RUnlock()
 		return broker.ErrNotConnected
 	}
-	m.RUnlock()
+	b.RUnlock()
 
 	select {
 	case <-ctx.Done():
@@ -141,9 +193,9 @@ func (m *Broker) publish(ctx context.Context, topic string, messages ...broker.M
 	default:
 	}
 
-	m.RLock()
-	subs, ok := m.subscribers[topic]
-	m.RUnlock()
+	b.RLock()
+	subs, ok := b.subscribers[topic]
+	b.RUnlock()
 	if !ok {
 		return nil
 	}
@@ -152,24 +204,28 @@ func (m *Broker) publish(ctx context.Context, topic string, messages ...broker.M
 
 	for _, sub := range subs {
 		switch s := sub.handler.(type) {
-		case broker.MessageHandler:
+		default:
+			if b.opts.Logger.V(logger.ErrorLevel) {
+				b.opts.Logger.Error(ctx, "broker  handler error", broker.ErrInvalidHandler)
+			}
+		case func(broker.Message) error:
 			for _, message := range messages {
 				if err = s(message); err == nil && sub.opts.AutoAck {
 					err = message.Ack()
 				}
 				if err != nil {
-					if m.opts.Logger.V(logger.ErrorLevel) {
-						m.opts.Logger.Error(m.opts.Context, "broker handler error", err)
+					if b.opts.Logger.V(logger.ErrorLevel) {
+						b.opts.Logger.Error(ctx, "broker handler error", err)
 					}
 				}
 			}
-		case broker.MessagesHandler:
+		case func([]broker.Message) error:
 			if err = s(messages); err == nil && sub.opts.AutoAck {
 				for _, message := range messages {
 					err = message.Ack()
 					if err != nil {
-						if m.opts.Logger.V(logger.ErrorLevel) {
-							m.opts.Logger.Error(m.opts.Context, "broker handler error", err)
+						if b.opts.Logger.V(logger.ErrorLevel) {
+							b.opts.Logger.Error(ctx, "broker handler error", err)
 						}
 					}
 				}
@@ -180,17 +236,21 @@ func (m *Broker) publish(ctx context.Context, topic string, messages ...broker.M
 	return nil
 }
 
-func (m *Broker) Subscribe(ctx context.Context, topic string, handler interface{}, opts ...broker.SubscribeOption) (broker.Subscriber, error) {
-	return m.funcSubscribe(ctx, topic, handler, opts...)
+func (b *Broker) Subscribe(ctx context.Context, topic string, handler interface{}, opts ...broker.SubscribeOption) (broker.Subscriber, error) {
+	return b.funcSubscribe(ctx, topic, handler, opts...)
 }
 
-func (m *Broker) fnSubscribe(ctx context.Context, topic string, handler interface{}, opts ...broker.SubscribeOption) (broker.Subscriber, error) {
-	m.RLock()
-	if !m.connected {
-		m.RUnlock()
+func (b *Broker) fnSubscribe(ctx context.Context, topic string, handler interface{}, opts ...broker.SubscribeOption) (broker.Subscriber, error) {
+	if err := broker.IsValidHandler(handler); err != nil {
+		return nil, err
+	}
+
+	b.RLock()
+	if !b.connected {
+		b.RUnlock()
 		return nil, broker.ErrNotConnected
 	}
-	m.RUnlock()
+	b.RUnlock()
 
 	sid, err := id.New()
 	if err != nil {
@@ -208,63 +268,47 @@ func (m *Broker) fnSubscribe(ctx context.Context, topic string, handler interfac
 		ctx:     ctx,
 	}
 
-	m.Lock()
-	m.subscribers[topic] = append(m.subscribers[topic], sub)
-	m.Unlock()
+	b.Lock()
+	b.subscribers[topic] = append(b.subscribers[topic], sub)
+	b.Unlock()
 
 	go func() {
 		<-sub.exit
-		m.Lock()
-		newSubscribers := make([]*Subscriber, 0, len(m.subscribers)-1)
-		for _, sb := range m.subscribers[topic] {
+		b.Lock()
+		newSubscribers := make([]*Subscriber, 0, len(b.subscribers)-1)
+		for _, sb := range b.subscribers[topic] {
 			if sb.id == sub.id {
 				continue
 			}
 			newSubscribers = append(newSubscribers, sb)
 		}
-		m.subscribers[topic] = newSubscribers
-		m.Unlock()
+		b.subscribers[topic] = newSubscribers
+		b.Unlock()
 	}()
 
 	return sub, nil
 }
 
-func (m *Broker) String() string {
+func (b *Broker) String() string {
 	return "memory"
 }
 
-func (m *Broker) Name() string {
-	return m.opts.Name
+func (b *Broker) Name() string {
+	return b.opts.Name
 }
 
-func (m *Broker) Live() bool {
+func (b *Broker) Live() bool {
 	return true
 }
 
-func (m *Broker) Ready() bool {
+func (b *Broker) Ready() bool {
 	return true
 }
 
-func (m *Broker) Health() bool {
+func (b *Broker) Health() bool {
 	return true
 }
 
-func (m *memoryMessage) Topic() string {
-	return m.topic
-}
-
-func (m *memoryMessage) Body() []byte {
-	return m.body
-}
-
-func (m *memoryMessage) Ack() error {
-	return nil
-}
-
-func (m *memoryMessage) Context() context.Context {
-	return m.ctx
-}
-
 func (m *Subscriber) Options() broker.SubscribeOptions {
 	return m.opts
 }
diff --git a/broker/memory/memory_test.go b/broker/memory/memory_test.go
index 936c3d7d..2d2fd4de 100644
--- a/broker/memory/memory_test.go
+++ b/broker/memory/memory_test.go
@@ -5,12 +5,23 @@ import (
 	"fmt"
 	"testing"
 
+	"go.uber.org/atomic"
 	"go.unistack.org/micro/v4/broker"
+	"go.unistack.org/micro/v4/codec"
 	"go.unistack.org/micro/v4/metadata"
 )
 
+type hldr struct {
+	c atomic.Int64
+}
+
+func (h *hldr) Handler(m broker.Message) error {
+	h.c.Add(1)
+	return nil
+}
+
 func TestMemoryBroker(t *testing.T) {
-	b := NewBroker()
+	b := NewBroker(broker.Codec("application/octet-stream", codec.NewCodec()))
 	ctx := context.Background()
 
 	if err := b.Init(); err != nil {
@@ -22,28 +33,27 @@ func TestMemoryBroker(t *testing.T) {
 	}
 
 	topic := "test"
-	count := 10
+	count := int64(10)
 
-	fn := func(_ broker.Message) error {
-		return nil
-	}
+	h := &hldr{}
 
-	sub, err := b.Subscribe(ctx, topic, fn)
+	sub, err := b.Subscribe(ctx, topic, h.Handler)
 	if err != nil {
 		t.Fatalf("Unexpected error subscribing %v", err)
 	}
 
-	msgs := make([]*broker.Message, 0, count)
-	for i := 0; i < count; i++ {
-		message, err := b.NewMessage(ctx, metadata.Pairs()
-			Header: map[string]string{
-				metadata.HeaderTopic: topic,
-				"foo":                "bar",
-				"id":                 fmt.Sprintf("%d", i),
-			},
+	for i := int64(0); i < count; i++ {
+		message, err := b.NewMessage(ctx,
+			metadata.Pairs(
+				"foo", "bar",
+				"id", fmt.Sprintf("%d", i),
+			),
 			[]byte(`"hello world"`),
+			broker.PublishContentType("application/octet-stream"),
+		)
+		if err != nil {
+			t.Fatal(err)
 		}
-		msgs = append(msgs, message)
 
 		if err := b.Publish(ctx, topic, message); err != nil {
 			t.Fatalf("Unexpected error publishing %d err: %v", i, err)
@@ -57,4 +67,8 @@ func TestMemoryBroker(t *testing.T) {
 	if err := b.Disconnect(ctx); err != nil {
 		t.Fatalf("Unexpected connect error %v", err)
 	}
+
+	if h.c.Load() != count {
+		t.Fatal("invalid messages count received")
+	}
 }
diff --git a/broker/noop.go b/broker/noop.go
index c3e84e18..4d160f3d 100644
--- a/broker/noop.go
+++ b/broker/noop.go
@@ -118,10 +118,6 @@ func (m *noopMessage) Context() context.Context {
 	return m.ctx
 }
 
-func (m *noopMessage) Error() error {
-	return nil
-}
-
 func (m *noopMessage) Topic() string {
 	return ""
 }
diff --git a/broker/options.go b/broker/options.go
index a5894794..a9900921 100644
--- a/broker/options.go
+++ b/broker/options.go
@@ -133,8 +133,8 @@ func Addrs(addrs ...string) Option {
 	}
 }
 
-// Codecs sets the codec used for encoding/decoding messages
-func Codecs(ct string, c codec.Codec) Option {
+// Codec sets the codec used for encoding/decoding messages
+func Codec(ct string, c codec.Codec) Option {
 	return func(o *Options) {
 		o.Codecs[ct] = c
 	}
diff --git a/broker/subscriber.go b/broker/subscriber.go
index 3470a5cd..bdced69c 100644
--- a/broker/subscriber.go
+++ b/broker/subscriber.go
@@ -1,6 +1,4 @@
-//go:build ignore
-
-package server
+package broker
 
 import (
 	"fmt"
@@ -10,7 +8,8 @@ import (
 )
 
 const (
-	subSig = "func(context.Context, interface{}) error"
+	messageSig  = "func(broker.Message) error"
+	messagesSig = "func([]broker.Message) error"
 )
 
 // Precompute the reflect type for error. Can't use error directly
@@ -33,31 +32,31 @@ func isExportedOrBuiltinType(t reflect.Type) bool {
 	return isExported(t.Name()) || t.PkgPath() == ""
 }
 
-// ValidateSubscriber func signature
-func ValidateSubscriber(sub Subscriber) error {
-	typ := reflect.TypeOf(sub.Subscriber())
+// IsValidHandler func signature
+func IsValidHandler(sub interface{}) error {
+	typ := reflect.TypeOf(sub)
 	var argType reflect.Type
 	switch typ.Kind() {
 	case reflect.Func:
 		name := "Func"
 		switch typ.NumIn() {
-		case 2:
-			argType = typ.In(1)
+		case 1:
+			argType = typ.In(0)
 		default:
-			return fmt.Errorf("subscriber %v takes wrong number of args: %v required signature %s", name, typ.NumIn(), subSig)
+			return fmt.Errorf("subscriber %v takes wrong number of args: %v required signature %s", name, typ.NumIn(), messageSig)
 		}
 		if !isExportedOrBuiltinType(argType) {
 			return fmt.Errorf("subscriber %v argument type not exported: %v", name, argType)
 		}
 		if typ.NumOut() != 1 {
 			return fmt.Errorf("subscriber %v has wrong number of return values: %v require signature %s",
-				name, typ.NumOut(), subSig)
+				name, typ.NumOut(), messageSig)
 		}
 		if returnType := typ.Out(0); returnType != typeOfError {
 			return fmt.Errorf("subscriber %v returns %v not error", name, returnType.String())
 		}
 	default:
-		hdlr := reflect.ValueOf(sub.Subscriber())
+		hdlr := reflect.ValueOf(sub)
 		name := reflect.Indirect(hdlr).Type().Name()
 
 		for m := 0; m < typ.NumMethod(); m++ {
@@ -67,7 +66,7 @@ func ValidateSubscriber(sub Subscriber) error {
 				argType = method.Type.In(2)
 			default:
 				return fmt.Errorf("subscriber %v.%v takes wrong number of args: %v required signature %s",
-					name, method.Name, method.Type.NumIn(), subSig)
+					name, method.Name, method.Type.NumIn(), messageSig)
 			}
 
 			if !isExportedOrBuiltinType(argType) {
@@ -76,7 +75,7 @@ func ValidateSubscriber(sub Subscriber) error {
 			if method.Type.NumOut() != 1 {
 				return fmt.Errorf(
 					"subscriber %v.%v has wrong number of return values: %v require signature %s",
-					name, method.Name, method.Type.NumOut(), subSig)
+					name, method.Name, method.Type.NumOut(), messageSig)
 			}
 			if returnType := method.Type.Out(0); returnType != typeOfError {
 				return fmt.Errorf("subscriber %v.%v returns %v not error", name, method.Name, returnType.String())
diff --git a/logger/slog/slog_test.go b/logger/slog/slog_test.go
index 18a24297..e8e6d353 100644
--- a/logger/slog/slog_test.go
+++ b/logger/slog/slog_test.go
@@ -412,9 +412,10 @@ func Test_WithContextAttrFunc(t *testing.T) {
 			}
 			attrs := make([]interface{}, 0, 10)
 			for k, v := range md {
-				switch k {
-				case "X-Request-Id", "Phone", "External-Id", "Source-Service", "X-App-Install-Id", "Client-Id", "Client-Ip":
-					attrs = append(attrs, strings.ToLower(k), v)
+				key := strings.ToLower(k)
+				switch key {
+				case "x-request-id", "phone", "external-Id", "source-service", "x-app-install-id", "client-id", "client-ip":
+					attrs = append(attrs, key, v[0])
 				}
 			}
 			return attrs
diff --git a/metadata/context.go b/metadata/context.go
deleted file mode 100644
index 471b144a..00000000
--- a/metadata/context.go
+++ /dev/null
@@ -1,181 +0,0 @@
-//go:build !exclude
-
-// Package metadata is a way of defining message headers
-package metadata
-
-import (
-	"context"
-)
-
-type (
-	mdIncomingKey struct{}
-	mdOutgoingKey struct{}
-	mdKey         struct{}
-)
-
-// FromIncomingContext returns metadata from incoming ctx
-// returned metadata shoud not be modified or race condition happens
-func FromIncomingContext(ctx context.Context) (Metadata, bool) {
-	if ctx == nil {
-		return nil, false
-	}
-	md, ok := ctx.Value(mdIncomingKey{}).(*rawMetadata)
-	if !ok || md.md == nil {
-		return nil, false
-	}
-	return md.md, ok
-}
-
-// MustIncomingContext returns metadata from incoming ctx
-// returned metadata shoud not be modified or race condition happens.
-// If metadata not exists panics.
-func MustIncomingContext(ctx context.Context) Metadata {
-	md, ok := FromIncomingContext(ctx)
-	if !ok {
-		panic("missing metadata")
-	}
-	return md
-}
-
-// FromOutgoingContext returns metadata from outgoing ctx
-// returned metadata shoud not be modified or race condition happens
-func FromOutgoingContext(ctx context.Context) (Metadata, bool) {
-	if ctx == nil {
-		return nil, false
-	}
-	md, ok := ctx.Value(mdOutgoingKey{}).(*rawMetadata)
-	if !ok || md.md == nil {
-		return nil, false
-	}
-	return md.md, ok
-}
-
-// MustOutgoingContext returns metadata from outgoing ctx
-// returned metadata shoud not be modified or race condition happens.
-// If metadata not exists panics.
-func MustOutgoingContext(ctx context.Context) Metadata {
-	md, ok := FromOutgoingContext(ctx)
-	if !ok {
-		panic("missing metadata")
-	}
-	return md
-}
-
-// FromContext returns metadata from the given context
-// returned metadata shoud not be modified or race condition happens
-func FromContext(ctx context.Context) (Metadata, bool) {
-	if ctx == nil {
-		return nil, false
-	}
-	md, ok := ctx.Value(mdKey{}).(*rawMetadata)
-	if !ok || md.md == nil {
-		return nil, false
-	}
-	return md.md, ok
-}
-
-// MustContext returns metadata from the given context
-// returned metadata shoud not be modified or race condition happens
-func MustContext(ctx context.Context) Metadata {
-	md, ok := FromContext(ctx)
-	if !ok {
-		panic("missing metadata")
-	}
-	return md
-}
-
-// NewContext creates a new context with the given metadata
-func NewContext(ctx context.Context, md Metadata) context.Context {
-	if ctx == nil {
-		ctx = context.Background()
-	}
-	return context.WithValue(ctx, mdKey{}, &rawMetadata{md})
-}
-
-// SetOutgoingContext modify outgoing context with given metadata
-func SetOutgoingContext(ctx context.Context, md Metadata) bool {
-	if ctx == nil {
-		return false
-	}
-	if omd, ok := ctx.Value(mdOutgoingKey{}).(*rawMetadata); ok {
-		omd.md = md
-		return true
-	}
-	return false
-}
-
-// SetIncomingContext modify incoming context with given metadata
-func SetIncomingContext(ctx context.Context, md Metadata) bool {
-	if ctx == nil {
-		return false
-	}
-	if omd, ok := ctx.Value(mdIncomingKey{}).(*rawMetadata); ok {
-		omd.md = md
-		return true
-	}
-	return false
-}
-
-// NewIncomingContext creates a new context with incoming metadata attached
-func NewIncomingContext(ctx context.Context, md Metadata) context.Context {
-	if ctx == nil {
-		ctx = context.Background()
-	}
-	return context.WithValue(ctx, mdIncomingKey{}, &rawMetadata{md})
-}
-
-// NewOutgoingContext creates a new context with outcoming metadata attached
-func NewOutgoingContext(ctx context.Context, md Metadata) context.Context {
-	if ctx == nil {
-		ctx = context.Background()
-	}
-	return context.WithValue(ctx, mdOutgoingKey{}, &rawMetadata{md})
-}
-
-// AppendOutgoingContext apends new md to context
-func AppendOutgoingContext(ctx context.Context, kv ...string) context.Context {
-	md, ok := Pairs(kv...)
-	if !ok {
-		return ctx
-	}
-	omd, ok := FromOutgoingContext(ctx)
-	if !ok {
-		return NewOutgoingContext(ctx, md)
-	}
-	for k, v := range md {
-		omd.Set(k, v)
-	}
-	return ctx
-}
-
-// AppendIncomingContext apends new md to context
-func AppendIncomingContext(ctx context.Context, kv ...string) context.Context {
-	md, ok := Pairs(kv...)
-	if !ok {
-		return ctx
-	}
-	omd, ok := FromIncomingContext(ctx)
-	if !ok {
-		return NewIncomingContext(ctx, md)
-	}
-	for k, v := range md {
-		omd.Set(k, v)
-	}
-	return ctx
-}
-
-// AppendContext apends new md to context
-func AppendContext(ctx context.Context, kv ...string) context.Context {
-	md, ok := Pairs(kv...)
-	if !ok {
-		return ctx
-	}
-	omd, ok := FromContext(ctx)
-	if !ok {
-		return NewContext(ctx, md)
-	}
-	for k, v := range md {
-		omd.Set(k, v)
-	}
-	return ctx
-}
diff --git a/metadata/context_test.go b/metadata/context_test.go
deleted file mode 100644
index deaa020a..00000000
--- a/metadata/context_test.go
+++ /dev/null
@@ -1,140 +0,0 @@
-package metadata
-
-import (
-	"context"
-	"testing"
-)
-
-func TestFromNilContext(t *testing.T) {
-	// nolint: staticcheck
-	c, ok := FromContext(nil)
-	if ok || c != nil {
-		t.Fatal("FromContext not works")
-	}
-}
-
-func TestNewNilContext(t *testing.T) {
-	// nolint: staticcheck
-	ctx := NewContext(nil, New(0))
-
-	c, ok := FromContext(ctx)
-	if c == nil || !ok {
-		t.Fatal("NewContext not works")
-	}
-}
-
-func TestFromContext(t *testing.T) {
-	ctx := context.WithValue(context.TODO(), mdKey{}, &rawMetadata{New(0)})
-
-	c, ok := FromContext(ctx)
-	if c == nil || !ok {
-		t.Fatal("FromContext not works")
-	}
-}
-
-func TestNewContext(t *testing.T) {
-	ctx := NewContext(context.TODO(), New(0))
-
-	c, ok := FromContext(ctx)
-	if c == nil || !ok {
-		t.Fatal("NewContext not works")
-	}
-}
-
-func TestFromIncomingContext(t *testing.T) {
-	ctx := context.WithValue(context.TODO(), mdIncomingKey{}, &rawMetadata{New(0)})
-
-	c, ok := FromIncomingContext(ctx)
-	if c == nil || !ok {
-		t.Fatal("FromIncomingContext not works")
-	}
-}
-
-func TestFromOutgoingContext(t *testing.T) {
-	ctx := context.WithValue(context.TODO(), mdOutgoingKey{}, &rawMetadata{New(0)})
-
-	c, ok := FromOutgoingContext(ctx)
-	if c == nil || !ok {
-		t.Fatal("FromOutgoingContext not works")
-	}
-}
-
-func TestSetIncomingContext(t *testing.T) {
-	md := New(1)
-	md.Set("key", "val")
-	ctx := context.WithValue(context.TODO(), mdIncomingKey{}, &rawMetadata{})
-	if !SetIncomingContext(ctx, md) {
-		t.Fatal("SetIncomingContext not works")
-	}
-	md, ok := FromIncomingContext(ctx)
-	if md == nil || !ok {
-		t.Fatal("SetIncomingContext not works")
-	} else if v, ok := md.Get("key"); !ok || v != "val" {
-		t.Fatal("SetIncomingContext not works")
-	}
-}
-
-func TestSetOutgoingContext(t *testing.T) {
-	md := New(1)
-	md.Set("key", "val")
-	ctx := context.WithValue(context.TODO(), mdOutgoingKey{}, &rawMetadata{})
-	if !SetOutgoingContext(ctx, md) {
-		t.Fatal("SetOutgoingContext not works")
-	}
-	md, ok := FromOutgoingContext(ctx)
-	if md == nil || !ok {
-		t.Fatal("SetOutgoingContext not works")
-	} else if v, ok := md.Get("key"); !ok || v != "val" {
-		t.Fatal("SetOutgoingContext not works")
-	}
-}
-
-func TestNewIncomingContext(t *testing.T) {
-	md := New(1)
-	md.Set("key", "val")
-	ctx := NewIncomingContext(context.TODO(), md)
-
-	c, ok := FromIncomingContext(ctx)
-	if c == nil || !ok {
-		t.Fatal("NewIncomingContext not works")
-	}
-}
-
-func TestNewOutgoingContext(t *testing.T) {
-	md := New(1)
-	md.Set("key", "val")
-	ctx := NewOutgoingContext(context.TODO(), md)
-
-	c, ok := FromOutgoingContext(ctx)
-	if c == nil || !ok {
-		t.Fatal("NewOutgoingContext not works")
-	}
-}
-
-func TestAppendIncomingContext(t *testing.T) {
-	md := New(1)
-	md.Set("key1", "val1")
-	ctx := AppendIncomingContext(context.TODO(), "key2", "val2")
-
-	nmd, ok := FromIncomingContext(ctx)
-	if nmd == nil || !ok {
-		t.Fatal("AppendIncomingContext not works")
-	}
-	if v, ok := nmd.Get("key2"); !ok || v != "val2" {
-		t.Fatal("AppendIncomingContext not works")
-	}
-}
-
-func TestAppendOutgoingContext(t *testing.T) {
-	md := New(1)
-	md.Set("key1", "val1")
-	ctx := AppendOutgoingContext(context.TODO(), "key2", "val2")
-
-	nmd, ok := FromOutgoingContext(ctx)
-	if nmd == nil || !ok {
-		t.Fatal("AppendOutgoingContext not works")
-	}
-	if v, ok := nmd.Get("key2"); !ok || v != "val2" {
-		t.Fatal("AppendOutgoingContext not works")
-	}
-}
diff --git a/metadata/headers.go b/metadata/headers.go
new file mode 100644
index 00000000..7e670eee
--- /dev/null
+++ b/metadata/headers.go
@@ -0,0 +1,19 @@
+// Package metadata is a way of defining message headers
+package metadata
+
+var (
+	// HeaderTopic is the header name that contains topic name
+	HeaderTopic = "Micro-Topic"
+	// HeaderContentType specifies content type of message
+	HeaderContentType = "Content-Type"
+	// HeaderEndpoint specifies endpoint in service
+	HeaderEndpoint = "Micro-Endpoint"
+	// HeaderService specifies service
+	HeaderService = "Micro-Service"
+	// HeaderTimeout specifies timeout of operation
+	HeaderTimeout = "Micro-Timeout"
+	// HeaderAuthorization specifies Authorization header
+	HeaderAuthorization = "Authorization"
+	// HeaderXRequestID specifies request id
+	HeaderXRequestID = "X-Request-Id"
+)
diff --git a/metadata/metadata.go b/metadata/metadata.go
index 4f67efbf..7664d0ea 100644
--- a/metadata/metadata.go
+++ b/metadata/metadata.go
@@ -1,43 +1,461 @@
-//go:build !exclude
-
-// Package metadata is a way of defining message headers
 package metadata
 
 import (
+	"context"
+	"fmt"
 	"net/textproto"
-	"sort"
 	"strings"
 )
 
-var (
-	// HeaderTopic is the header name that contains topic name
-	HeaderTopic = "Micro-Topic"
-	// HeaderContentType specifies content type of message
-	HeaderContentType = "Content-Type"
-	// HeaderEndpoint specifies endpoint in service
-	HeaderEndpoint = "Micro-Endpoint"
-	// HeaderService specifies service
-	HeaderService = "Micro-Service"
-	// HeaderTimeout specifies timeout of operation
-	HeaderTimeout = "Micro-Timeout"
-	// HeaderAuthorization specifies Authorization header
-	HeaderAuthorization = "Authorization"
-	// HeaderXRequestID specifies request id
-	HeaderXRequestID = "X-Request-Id"
-)
-
-// Metadata is our way of representing request headers internally.
-// They're used at the RPC level and translate back and forth
-// from Transport headers.
-type Metadata map[string]string
-
-type rawMetadata struct {
-	md Metadata
-}
-
 // defaultMetadataSize used when need to init new Metadata
 var defaultMetadataSize = 2
 
+// Metadata is a mapping from metadata keys to values. Users should use the following
+// two convenience functions New and Pairs to generate Metadata.
+type Metadata map[string][]string
+
+// New creates an zero Metadata.
+func New(l int) Metadata {
+	if l == 0 {
+		l = defaultMetadataSize
+	}
+	md := make(Metadata, l)
+	return md
+}
+
+// NewWithMetadata creates an Metadata from a given key-value map.
+func NewWithMetadata(m map[string]string) Metadata {
+	md := make(Metadata, len(m))
+	for key, val := range m {
+		md[key] = append(md[key], val)
+	}
+	return md
+}
+
+// Pairs returns an Metadata formed by the mapping of key, value ...
+// Pairs panics if len(kv) is odd.
+func Pairs(kv ...string) Metadata {
+	if len(kv)%2 == 1 {
+		panic(fmt.Sprintf("metadata: Pairs got the odd number of input pairs for metadata: %d", len(kv)))
+	}
+	md := make(Metadata, len(kv)/2)
+	for i := 0; i < len(kv); i += 2 {
+		md[kv[i]] = append(md[kv[i]], kv[i+1])
+	}
+	return md
+}
+
+// Len returns the number of items in Metadata.
+func (md Metadata) Len() int {
+	return len(md)
+}
+
+// Copy returns a copy of Metadata.
+func Copy(src Metadata) Metadata {
+	out := make(Metadata, len(src))
+	for k, v := range src {
+		out[k] = copyOf(v)
+	}
+	return out
+}
+
+// Copy returns a copy of Metadata.
+func (md Metadata) Copy() Metadata {
+	out := make(Metadata, len(md))
+	for k, v := range md {
+		out[k] = copyOf(v)
+	}
+	return out
+}
+
+// AsHTTP1 returns a copy of Metadata
+// with CanonicalMIMEHeaderKey.
+func (md Metadata) AsHTTP1() map[string][]string {
+	out := make(map[string][]string, len(md))
+	for k, v := range md {
+		out[textproto.CanonicalMIMEHeaderKey(k)] = copyOf(v)
+	}
+	return out
+}
+
+// AsHTTP1 returns a copy of Metadata
+// with strings.ToLower.
+func (md Metadata) AsHTTP2() map[string][]string {
+	out := make(map[string][]string, len(md))
+	for k, v := range md {
+		out[strings.ToLower(k)] = copyOf(v)
+	}
+	return out
+}
+
+// CopyTo copies Metadata to out.
+func (md Metadata) CopyTo(out Metadata) {
+	for k, v := range md {
+		out[k] = copyOf(v)
+	}
+}
+
+// Get obtains the values for a given key.
+func (md Metadata) MustGet(k string) []string {
+	v, ok := md.Get(k)
+	if !ok {
+		panic("missing metadata key")
+	}
+	return v
+}
+
+// Get obtains the values for a given key.
+func (md Metadata) Get(k string) ([]string, bool) {
+	v, ok := md[k]
+	if !ok {
+		v, ok = md[strings.ToLower(k)]
+	}
+	if !ok {
+		v, ok = md[textproto.CanonicalMIMEHeaderKey(k)]
+	}
+	return v, ok
+}
+
+// MustGetJoined obtains the values for a given key
+// with joined values with "," symbol
+func (md Metadata) MustGetJoined(k string) string {
+	v, ok := md.GetJoined(k)
+	if !ok {
+		panic("missing metadata key")
+	}
+	return v
+}
+
+// GetJoined obtains the values for a given key
+// with joined values with "," symbol
+func (md Metadata) GetJoined(k string) (string, bool) {
+	v, ok := md.Get(k)
+	if !ok {
+		return "", ok
+	}
+	return strings.Join(v, ","), true
+}
+
+// Set sets the value of a given key with a slice of values.
+func (md Metadata) Add(key string, vals ...string) {
+	if len(vals) == 0 {
+		return
+	}
+	md[key] = vals
+}
+
+// Set sets the value of a given key with a slice of values.
+func (md Metadata) Set(kvs ...string) {
+	if len(kvs)%2 == 1 {
+		panic(fmt.Sprintf("metadata: Set got an odd number of input pairs for metadata: %d", len(kvs)))
+	}
+
+	for i := 0; i < len(kvs); i += 2 {
+		md[kvs[i]] = append(md[kvs[i]], kvs[i+1])
+	}
+}
+
+// Append adds the values to key k, not overwriting what was already stored at
+// that key.
+func (md Metadata) Append(key string, vals ...string) {
+	if len(vals) == 0 {
+		return
+	}
+	md[key] = append(md[key], vals...)
+}
+
+// Del removes the values for a given keys k.
+func (md Metadata) Del(k ...string) {
+	for i := range k {
+		delete(md, k[i])
+		delete(md, strings.ToLower(k[i]))
+		delete(md, textproto.CanonicalMIMEHeaderKey(k[i]))
+	}
+}
+
+// Join joins any number of Metadatas into a single Metadata.
+//
+// The order of values for each key is determined by the order in which the Metadatas
+// containing those values are presented to Join.
+func Join(mds ...Metadata) Metadata {
+	out := Metadata{}
+	for _, Metadata := range mds {
+		for k, v := range Metadata {
+			out[k] = append(out[k], v...)
+		}
+	}
+	return out
+}
+
+type (
+	metadataIncomingKey struct{}
+	metadataOutgoingKey struct{}
+	metadataCurrentKey  struct{}
+)
+
+// NewContext creates a new context with Metadata attached. Metadata must
+// not be modified after calling this function.
+func NewContext(ctx context.Context, md Metadata) context.Context {
+	return context.WithValue(ctx, metadataCurrentKey{}, rawMetadata{md: md})
+}
+
+// NewIncomingContext creates a new context with incoming Metadata attached. Metadata must
+// not be modified after calling this function.
+func NewIncomingContext(ctx context.Context, md Metadata) context.Context {
+	return context.WithValue(ctx, metadataIncomingKey{}, rawMetadata{md: md})
+}
+
+// NewOutgoingContext creates a new context with outgoing Metadata attached. If used
+// in conjunction with AppendOutgoingContext, NewOutgoingContext will
+// overwrite any previously-appended metadata. Metadata must not be modified after
+// calling this function.
+func NewOutgoingContext(ctx context.Context, md Metadata) context.Context {
+	return context.WithValue(ctx, metadataOutgoingKey{}, rawMetadata{md: md})
+}
+
+// AppendContext returns a new context with the provided kv merged
+// with any existing metadata in the context. Please refer to the documentation
+// of Pairs for a description of kv.
+func AppendContext(ctx context.Context, kv ...string) context.Context {
+	if len(kv)%2 == 1 {
+		panic(fmt.Sprintf("metadata: AppendContext got an odd number of input pairs for metadata: %d", len(kv)))
+	}
+	md, _ := ctx.Value(metadataCurrentKey{}).(rawMetadata)
+	added := make([][]string, len(md.added)+1)
+	copy(added, md.added)
+	kvCopy := make([]string, 0, len(kv))
+	for i := 0; i < len(kv); i += 2 {
+		kvCopy = append(kvCopy, strings.ToLower(kv[i]), kv[i+1])
+	}
+	added[len(added)-1] = kvCopy
+	return context.WithValue(ctx, metadataCurrentKey{}, rawMetadata{md: md.md, added: added})
+}
+
+// AppendIncomingContext returns a new context with the provided kv merged
+// with any existing metadata in the context. Please refer to the documentation
+// of Pairs for a description of kv.
+func AppendIncomingContext(ctx context.Context, kv ...string) context.Context {
+	if len(kv)%2 == 1 {
+		panic(fmt.Sprintf("metadata: AppendIncomingContext got an odd number of input pairs for metadata: %d", len(kv)))
+	}
+	md, _ := ctx.Value(metadataIncomingKey{}).(rawMetadata)
+	added := make([][]string, len(md.added)+1)
+	copy(added, md.added)
+	kvCopy := make([]string, 0, len(kv))
+	for i := 0; i < len(kv); i += 2 {
+		kvCopy = append(kvCopy, strings.ToLower(kv[i]), kv[i+1])
+	}
+	added[len(added)-1] = kvCopy
+	return context.WithValue(ctx, metadataIncomingKey{}, rawMetadata{md: md.md, added: added})
+}
+
+// AppendOutgoingContext returns a new context with the provided kv merged
+// with any existing metadata in the context. Please refer to the documentation
+// of Pairs for a description of kv.
+func AppendOutgoingContext(ctx context.Context, kv ...string) context.Context {
+	if len(kv)%2 == 1 {
+		panic(fmt.Sprintf("metadata: AppendOutgoingContext got an odd number of input pairs for metadata: %d", len(kv)))
+	}
+	md, _ := ctx.Value(metadataOutgoingKey{}).(rawMetadata)
+	added := make([][]string, len(md.added)+1)
+	copy(added, md.added)
+	kvCopy := make([]string, 0, len(kv))
+	for i := 0; i < len(kv); i += 2 {
+		kvCopy = append(kvCopy, strings.ToLower(kv[i]), kv[i+1])
+	}
+	added[len(added)-1] = kvCopy
+	return context.WithValue(ctx, metadataOutgoingKey{}, rawMetadata{md: md.md, added: added})
+}
+
+// FromContext returns the metadata in ctx if it exists.
+func FromContext(ctx context.Context) (Metadata, bool) {
+	raw, ok := ctx.Value(metadataCurrentKey{}).(rawMetadata)
+	if !ok {
+		return nil, false
+	}
+	metadataSize := len(raw.md)
+	for i := range raw.added {
+		metadataSize += len(raw.added[i]) / 2
+	}
+
+	out := make(Metadata, metadataSize)
+	for k, v := range raw.md {
+		out[k] = copyOf(v)
+	}
+	for _, added := range raw.added {
+		if len(added)%2 == 1 {
+			panic(fmt.Sprintf("metadata: FromContext got an odd number of input pairs for metadata: %d", len(added)))
+		}
+
+		for i := 0; i < len(added); i += 2 {
+			out[added[i]] = append(out[added[i]], added[i+1])
+		}
+	}
+	return out, true
+}
+
+// MustContext returns the metadata in ctx.
+func MustContext(ctx context.Context) Metadata {
+	md, ok := FromContext(ctx)
+	if !ok {
+		panic("missing metadata")
+	}
+	return md
+}
+
+// FromIncomingContext returns the incoming metadata in ctx if it exists.
+func FromIncomingContext(ctx context.Context) (Metadata, bool) {
+	raw, ok := ctx.Value(metadataIncomingKey{}).(rawMetadata)
+	if !ok {
+		return nil, false
+	}
+	metadataSize := len(raw.md)
+	for i := range raw.added {
+		metadataSize += len(raw.added[i]) / 2
+	}
+
+	out := make(Metadata, metadataSize)
+	for k, v := range raw.md {
+		out[k] = copyOf(v)
+	}
+	for _, added := range raw.added {
+		if len(added)%2 == 1 {
+			panic(fmt.Sprintf("metadata: FromIncomingContext got an odd number of input pairs for metadata: %d", len(added)))
+		}
+
+		for i := 0; i < len(added); i += 2 {
+			out[added[i]] = append(out[added[i]], added[i+1])
+		}
+	}
+	return out, true
+}
+
+// MustIncomingContext returns the incoming metadata in ctx.
+func MustIncomingContext(ctx context.Context) Metadata {
+	md, ok := FromIncomingContext(ctx)
+	if !ok {
+		panic("missing metadata")
+	}
+	return md
+}
+
+// ValueFromIncomingContext returns the metadata value corresponding to the metadata
+// key from the incoming metadata if it exists. Keys are matched in a case insensitive
+// manner.
+func ValueFromIncomingContext(ctx context.Context, key string) []string {
+	raw, ok := ctx.Value(metadataIncomingKey{}).(rawMetadata)
+	if !ok {
+		return nil
+	}
+
+	if v, ok := raw.md[key]; ok {
+		return copyOf(v)
+	}
+	for k, v := range raw.md {
+		// Case insensitive comparison: Metadata is a map, and there's no guarantee
+		// that the Metadata attached to the context is created using our helper
+		// functions.
+		if strings.EqualFold(k, key) {
+			return copyOf(v)
+		}
+	}
+	return nil
+}
+
+// ValueFromCurrentContext returns the metadata value corresponding to the metadata
+// key from the incoming metadata if it exists. Keys are matched in a case insensitive
+// manner.
+func ValueFromCurrentContext(ctx context.Context, key string) []string {
+	md, ok := ctx.Value(metadataCurrentKey{}).(rawMetadata)
+	if !ok {
+		return nil
+	}
+
+	if v, ok := md.md[key]; ok {
+		return copyOf(v)
+	}
+	for k, v := range md.md {
+		// Case insensitive comparison: Metadata is a map, and there's no guarantee
+		// that the Metadata attached to the context is created using our helper
+		// functions.
+		if strings.EqualFold(k, key) {
+			return copyOf(v)
+		}
+	}
+	return nil
+}
+
+// MustOutgoingContext returns the outgoing metadata in ctx.
+func MustOutgoingContext(ctx context.Context) Metadata {
+	md, ok := FromOutgoingContext(ctx)
+	if !ok {
+		panic("missing metadata")
+	}
+	return md
+}
+
+// ValueFromOutgoingContext returns the metadata value corresponding to the metadata
+// key from the incoming metadata if it exists. Keys are matched in a case insensitive
+// manner.
+func ValueFromOutgoingContext(ctx context.Context, key string) []string {
+	md, ok := ctx.Value(metadataOutgoingKey{}).(rawMetadata)
+	if !ok {
+		return nil
+	}
+
+	if v, ok := md.md[key]; ok {
+		return copyOf(v)
+	}
+	for k, v := range md.md {
+		// Case insensitive comparison: Metadata is a map, and there's no guarantee
+		// that the Metadata attached to the context is created using our helper
+		// functions.
+		if strings.EqualFold(k, key) {
+			return copyOf(v)
+		}
+	}
+	return nil
+}
+
+func copyOf(v []string) []string {
+	vals := make([]string, len(v))
+	copy(vals, v)
+	return vals
+}
+
+// FromOutgoingContext returns the outgoing metadata in ctx if it exists.
+func FromOutgoingContext(ctx context.Context) (Metadata, bool) {
+	raw, ok := ctx.Value(metadataOutgoingKey{}).(rawMetadata)
+	if !ok {
+		return nil, false
+	}
+
+	metadataSize := len(raw.md)
+	for i := range raw.added {
+		metadataSize += len(raw.added[i]) / 2
+	}
+
+	out := make(Metadata, metadataSize)
+	for k, v := range raw.md {
+		out[k] = copyOf(v)
+	}
+	for _, added := range raw.added {
+		if len(added)%2 == 1 {
+			panic(fmt.Sprintf("metadata: FromOutgoingContext got an odd number of input pairs for metadata: %d", len(added)))
+		}
+
+		for i := 0; i < len(added); i += 2 {
+			out[added[i]] = append(out[added[i]], added[i+1])
+		}
+	}
+	return out, ok
+}
+
+type rawMetadata struct {
+	md    Metadata
+	added [][]string
+}
+
 // Iterator used to iterate over metadata with order
 type Iterator struct {
 	md   Metadata
@@ -46,6 +464,7 @@ type Iterator struct {
 	cnt  int
 }
 
+/*
 // Next advance iterator to next element
 func (iter *Iterator) Next(k, v *string) bool {
 	if iter.cur+1 > iter.cnt {
@@ -53,122 +472,19 @@ func (iter *Iterator) Next(k, v *string) bool {
 	}
 
 	*k = iter.keys[iter.cur]
-	*v = iter.md[*k]
+	*v = iter.Metadata[*k]
 	iter.cur++
 	return true
 }
 
 // Iterator returns the itarator for metadata in sorted order
-func (md Metadata) Iterator() *Iterator {
-	iter := &Iterator{md: md, cnt: len(md)}
+func (Metadata Metadata) Iterator() *Iterator {
+	iter := &Iterator{Metadata: Metadata, cnt: len(Metadata)}
 	iter.keys = make([]string, 0, iter.cnt)
-	for k := range md {
+	for k := range Metadata {
 		iter.keys = append(iter.keys, k)
 	}
 	sort.Strings(iter.keys)
 	return iter
 }
-
-func (md Metadata) MustGet(key string) string {
-	val, ok := md.Get(key)
-	if !ok {
-		panic("missing metadata key")
-	}
-	return val
-}
-
-// Len returns the number of items.
-func (md Metadata) Len() int {
-	return len(md)
-}
-
-// Get returns value from metadata by key
-func (md Metadata) Get(key string) (string, bool) {
-	// fast path
-	val, ok := md[key]
-	if !ok {
-		// slow path
-		val, ok = md[textproto.CanonicalMIMEHeaderKey(key)]
-		if !ok {
-			val, ok = md[strings.ToLower(key)]
-		}
-	}
-	return val, ok
-}
-
-// Set is used to store value in metadata
-func (md Metadata) Set(kv ...string) {
-	if len(kv)%2 == 1 {
-		kv = kv[:len(kv)-1]
-	}
-	for idx := 0; idx < len(kv); idx += 2 {
-		md[textproto.CanonicalMIMEHeaderKey(kv[idx])] = kv[idx+1]
-	}
-}
-
-// Del is used to remove value from metadata
-func (md Metadata) Del(keys ...string) {
-	for _, key := range keys {
-		// fast path
-		delete(md, key)
-		// slow path
-		delete(md, textproto.CanonicalMIMEHeaderKey(key))
-		// very slow path
-		delete(md, strings.ToLower(key))
-	}
-}
-
-// Copy makes a copy of the metadata
-func (md Metadata) CopyTo(dst Metadata) {
-	for k, v := range md {
-		dst[k] = v
-	}
-}
-
-// Copy makes a copy of the metadata
-func Copy(md Metadata, exclude ...string) Metadata {
-	nmd := New(len(md))
-	for k, v := range md {
-		nmd[k] = v
-	}
-	nmd.Del(exclude...)
-	return nmd
-}
-
-// New return new sized metadata
-func New(size int) Metadata {
-	if size == 0 {
-		size = defaultMetadataSize
-	}
-	return make(Metadata, size)
-}
-
-// Merge merges metadata to existing metadata, overwriting if specified
-func Merge(omd Metadata, mmd Metadata, overwrite bool) Metadata {
-	var ok bool
-	nmd := Copy(omd)
-	for key, val := range mmd {
-		_, ok = nmd[key]
-		switch {
-		case ok && !overwrite:
-			continue
-		case val != "":
-			nmd[key] = val
-		case ok && val == "":
-			nmd.Del(key)
-		}
-	}
-	return nmd
-}
-
-// Pairs from which metadata created
-func Pairs(kv ...string) Metadata {
-	if len(kv)%2 == 1 {
-		return nil
-	}
-	md := New(len(kv) / 2)
-	for idx := 0; idx < len(kv); idx += 2 {
-		md[kv[idx]] = kv[idx+1]
-	}
-	return md
-}
+*/
diff --git a/metadata/metadata_test.go b/metadata/metadata_test.go
index 47d53cf9..0891021f 100644
--- a/metadata/metadata_test.go
+++ b/metadata/metadata_test.go
@@ -5,10 +5,21 @@ import (
 	"testing"
 )
 
+/*
+func TestAppendOutgoingContextModify(t *testing.T) {
+	md := Pairs("key1", "val1")
+	ctx := NewOutgoingContext(context.TODO(), md)
+	nctx := AppendOutgoingContext(ctx, "key1", "val3", "key2", "val2")
+	_ = nctx
+	omd := MustOutgoingContext(nctx)
+	fmt.Printf("%#+v\n", omd)
+}
+*/
+
 func TestLowercase(t *testing.T) {
 	md := New(1)
-	md["x-request-id"] = "12345"
-	v, ok := md.Get("X-Request-Id")
+	md["x-request-id"] = []string{"12345"}
+	v, ok := md.GetJoined("X-Request-Id")
 	if !ok || v == "" {
 		t.Fatalf("metadata invalid %#+v", md)
 	}
@@ -38,15 +49,12 @@ func TestMultipleUsage(t *testing.T) {
 
 func TestMetadataSetMultiple(t *testing.T) {
 	md := New(4)
-	md.Set("key1", "val1", "key2", "val2", "key3")
+	md.Set("key1", "val1", "key2", "val2")
 
-	if v, ok := md.Get("key1"); !ok || v != "val1" {
+	if v, ok := md.GetJoined("key1"); !ok || v != "val1" {
 		t.Fatalf("invalid kv %#+v", md)
 	}
-	if v, ok := md.Get("key2"); !ok || v != "val2" {
-		t.Fatalf("invalid kv %#+v", md)
-	}
-	if _, ok := md.Get("key3"); ok {
+	if v, ok := md.GetJoined("key2"); !ok || v != "val2" {
 		t.Fatalf("invalid kv %#+v", md)
 	}
 }
@@ -64,22 +72,12 @@ func TestAppend(t *testing.T) {
 }
 
 func TestPairs(t *testing.T) {
-	md, ok := Pairs("key1", "val1", "key2", "val2")
-	if !ok {
-		t.Fatal("odd number of kv")
-	}
-	if _, ok = md.Get("key1"); !ok {
+	md := Pairs("key1", "val1", "key2", "val2")
+	if _, ok := md.Get("key1"); !ok {
 		t.Fatal("key1 not found")
 	}
 }
 
-func testCtx(ctx context.Context) {
-	md := New(2)
-	md.Set("Key1", "Val1_new")
-	md.Set("Key3", "Val3")
-	SetOutgoingContext(ctx, md)
-}
-
 func TestPassing(t *testing.T) {
 	ctx := context.TODO()
 	md1 := New(2)
@@ -87,37 +85,24 @@ func TestPassing(t *testing.T) {
 	md1.Set("Key2", "Val2")
 
 	ctx = NewIncomingContext(ctx, md1)
-	testCtx(ctx)
+
 	_, ok := FromOutgoingContext(ctx)
 	if ok {
 		t.Fatalf("create outgoing context")
 	}
 
-	ctx = NewOutgoingContext(ctx, New(1))
-	testCtx(ctx)
+	ctx = NewOutgoingContext(ctx, md1)
+
 	md, ok := FromOutgoingContext(ctx)
 	if !ok {
 		t.Fatalf("missing metadata from outgoing context")
 	}
-	if v, ok := md.Get("Key1"); !ok || v != "Val1_new" {
+	if v, ok := md.Get("Key1"); !ok || v[0] != "Val1" {
 		t.Fatalf("invalid metadata value %#+v", md)
 	}
 }
 
-func TestMerge(t *testing.T) {
-	omd := Metadata{
-		"key1": "val1",
-	}
-	mmd := Metadata{
-		"key2": "val2",
-	}
-
-	nmd := Merge(omd, mmd, true)
-	if len(nmd) != 2 {
-		t.Fatalf("merge failed: %v", nmd)
-	}
-}
-
+/*
 func TestIterator(_ *testing.T) {
 	md := Metadata{
 		"1Last":   "last",
@@ -132,24 +117,25 @@ func TestIterator(_ *testing.T) {
 		// fmt.Printf("k: %s, v: %s\n", k, v)
 	}
 }
+*/
 
 func TestMedataCanonicalKey(t *testing.T) {
 	md := New(1)
 	md.Set("x-request-id", "12345")
-	v, ok := md.Get("x-request-id")
+	v, ok := md.GetJoined("x-request-id")
 	if !ok {
 		t.Fatalf("failed to get x-request-id")
 	} else if v != "12345" {
 		t.Fatalf("invalid metadata value: %s != %s", "12345", v)
 	}
 
-	v, ok = md.Get("X-Request-Id")
+	v, ok = md.GetJoined("X-Request-Id")
 	if !ok {
 		t.Fatalf("failed to get x-request-id")
 	} else if v != "12345" {
 		t.Fatalf("invalid metadata value: %s != %s", "12345", v)
 	}
-	v, ok = md.Get("X-Request-ID")
+	v, ok = md.GetJoined("X-Request-ID")
 	if !ok {
 		t.Fatalf("failed to get x-request-id")
 	} else if v != "12345" {
@@ -162,7 +148,7 @@ func TestMetadataSet(t *testing.T) {
 
 	md.Set("Key", "val")
 
-	val, ok := md.Get("Key")
+	val, ok := md.GetJoined("Key")
 	if !ok {
 		t.Fatal("key Key not found")
 	}
@@ -173,8 +159,8 @@ func TestMetadataSet(t *testing.T) {
 
 func TestMetadataDelete(t *testing.T) {
 	md := Metadata{
-		"Foo": "bar",
-		"Baz": "empty",
+		"Foo": []string{"bar"},
+		"Baz": []string{"empty"},
 	}
 
 	md.Del("Baz")
@@ -184,25 +170,16 @@ func TestMetadataDelete(t *testing.T) {
 	}
 }
 
-func TestNilContext(t *testing.T) {
-	var ctx context.Context
-
-	_, ok := FromContext(ctx)
-	if ok {
-		t.Fatal("nil context")
-	}
-}
-
 func TestMetadataCopy(t *testing.T) {
 	md := Metadata{
-		"Foo": "bar",
-		"Bar": "baz",
+		"Foo": []string{"bar"},
+		"Bar": []string{"baz"},
 	}
 
 	cp := Copy(md)
 
 	for k, v := range md {
-		if cv := cp[k]; cv != v {
+		if cv := cp[k]; cv[0] != v[0] {
 			t.Fatalf("Got %s:%s for %s:%s", k, cv, k, v)
 		}
 	}
@@ -210,7 +187,7 @@ func TestMetadataCopy(t *testing.T) {
 
 func TestMetadataContext(t *testing.T) {
 	md := Metadata{
-		"Foo": "bar",
+		"Foo": []string{"bar"},
 	}
 
 	ctx := NewContext(context.TODO(), md)
@@ -220,7 +197,7 @@ func TestMetadataContext(t *testing.T) {
 		t.Errorf("Unexpected error retrieving metadata, got %t", ok)
 	}
 
-	if emd["Foo"] != md["Foo"] {
+	if emd["Foo"][0] != md["Foo"][0] {
 		t.Errorf("Expected key: %s val: %s, got key: %s val: %s", "Foo", md["Foo"], "Foo", emd["Foo"])
 	}
 
@@ -229,13 +206,88 @@ func TestMetadataContext(t *testing.T) {
 	}
 }
 
-func TestCopy(t *testing.T) {
-	md := New(2)
-	md.Set("key1", "val1", "key2", "val2")
-	nmd := Copy(md, "key2")
-	if len(nmd) != 1 {
-		t.Fatal("Copy exclude not works")
-	} else if nmd["Key1"] != "val1" {
-		t.Fatal("Copy exclude not works")
+func TestFromContext(t *testing.T) {
+	ctx := context.WithValue(context.TODO(), metadataCurrentKey{}, rawMetadata{md: New(0)})
+
+	c, ok := FromContext(ctx)
+	if c == nil || !ok {
+		t.Fatal("FromContext not works")
+	}
+}
+
+func TestNewContext(t *testing.T) {
+	ctx := NewContext(context.TODO(), New(0))
+
+	c, ok := FromContext(ctx)
+	if c == nil || !ok {
+		t.Fatal("NewContext not works")
+	}
+}
+
+func TestFromIncomingContext(t *testing.T) {
+	ctx := context.WithValue(context.TODO(), metadataIncomingKey{}, rawMetadata{md: New(0)})
+
+	c, ok := FromIncomingContext(ctx)
+	if c == nil || !ok {
+		t.Fatal("FromIncomingContext not works")
+	}
+}
+
+func TestFromOutgoingContext(t *testing.T) {
+	ctx := context.WithValue(context.TODO(), metadataOutgoingKey{}, rawMetadata{md: New(0)})
+
+	c, ok := FromOutgoingContext(ctx)
+	if c == nil || !ok {
+		t.Fatal("FromOutgoingContext not works")
+	}
+}
+
+func TestNewIncomingContext(t *testing.T) {
+	md := New(1)
+	md.Set("key", "val")
+	ctx := NewIncomingContext(context.TODO(), md)
+
+	c, ok := FromIncomingContext(ctx)
+	if c == nil || !ok {
+		t.Fatal("NewIncomingContext not works")
+	}
+}
+
+func TestNewOutgoingContext(t *testing.T) {
+	md := New(1)
+	md.Set("key", "val")
+	ctx := NewOutgoingContext(context.TODO(), md)
+
+	c, ok := FromOutgoingContext(ctx)
+	if c == nil || !ok {
+		t.Fatal("NewOutgoingContext not works")
+	}
+}
+
+func TestAppendIncomingContext(t *testing.T) {
+	md := New(1)
+	md.Set("key1", "val1")
+	ctx := AppendIncomingContext(context.TODO(), "key2", "val2")
+
+	nmd, ok := FromIncomingContext(ctx)
+	if nmd == nil || !ok {
+		t.Fatal("AppendIncomingContext not works")
+	}
+	if v, ok := nmd.GetJoined("key2"); !ok || v != "val2" {
+		t.Fatal("AppendIncomingContext not works")
+	}
+}
+
+func TestAppendOutgoingContext(t *testing.T) {
+	md := New(1)
+	md.Set("key1", "val1")
+	ctx := AppendOutgoingContext(context.TODO(), "key2", "val2")
+
+	nmd, ok := FromOutgoingContext(ctx)
+	if nmd == nil || !ok {
+		t.Fatal("AppendOutgoingContext not works")
+	}
+	if v, ok := nmd.GetJoined("key2"); !ok || v != "val2" {
+		t.Fatal("AppendOutgoingContext not works")
 	}
 }
diff --git a/micro_test.go b/micro_test.go
index f92c223e..f8990f6f 100644
--- a/micro_test.go
+++ b/micro_test.go
@@ -8,6 +8,7 @@ import (
 
 	"go.unistack.org/micro/v4/broker"
 	"go.unistack.org/micro/v4/fsm"
+	"go.unistack.org/micro/v4/metadata"
 )
 
 func TestAs(t *testing.T) {
@@ -61,6 +62,8 @@ func TestAs(t *testing.T) {
 	}
 }
 
+var _ broker.Broker = (*bro)(nil)
+
 type bro struct {
 	name string
 }
@@ -87,23 +90,18 @@ func (p *bro) Connect(_ context.Context) error { return nil }
 // Disconnect disconnect from broker
 func (p *bro) Disconnect(_ context.Context) error { return nil }
 
-// Publish message, msg can be single broker.Message or []broker.Message
-func (p *bro) Publish(_ context.Context, _ string, _ *broker.Message, _ ...broker.PublishOption) error {
-	return nil
-}
-
-// BatchPublish messages to broker with multiple topics
-func (p *bro) BatchPublish(_ context.Context, _ []*broker.Message, _ ...broker.PublishOption) error {
-	return nil
-}
-
-// BatchSubscribe subscribes to topic messages via handler
-func (p *bro) BatchSubscribe(_ context.Context, _ string, _ broker.BatchHandler, _ ...broker.SubscribeOption) (broker.Subscriber, error) {
+// NewMessage creates new message
+func (p *bro) NewMessage(_ context.Context, _ metadata.Metadata, _ interface{}, _ ...broker.PublishOption) (broker.Message, error) {
 	return nil, nil
 }
 
+// Publish message, msg can be single broker.Message or []broker.Message
+func (p *bro) Publish(_ context.Context, _ string, _ ...broker.Message) error {
+	return nil
+}
+
 // Subscribe subscribes to topic message via handler
-func (p *bro) Subscribe(_ context.Context, _ string, _ broker.Handler, _ ...broker.SubscribeOption) (broker.Subscriber, error) {
+func (p *bro) Subscribe(_ context.Context, _ string, _ interface{}, _ ...broker.SubscribeOption) (broker.Subscriber, error) {
 	return nil, nil
 }
 
diff --git a/register/memory/memory.go b/register/memory/memory.go
index 43518e98..ebf93178 100644
--- a/register/memory/memory.go
+++ b/register/memory/memory.go
@@ -6,9 +6,10 @@ import (
 	"sync"
 	"time"
 
-	"go.unistack.org/micro/v4/logger"
-	"go.unistack.org/micro/v4/register"
-	"go.unistack.org/micro/v4/util/id"
+	"go.unistack.org/micro/v3/logger"
+	"go.unistack.org/micro/v3/metadata"
+	"go.unistack.org/micro/v3/register"
+	"go.unistack.org/micro/v3/util/id"
 )
 
 var (
@@ -23,10 +24,9 @@ type node struct {
 }
 
 type record struct {
-	Name     string
-	Version  string
-	Metadata map[string]string
-	Nodes    map[string]*node
+	Name    string
+	Version string
+	Nodes   map[string]*node
 }
 
 type memory struct {
@@ -160,19 +160,14 @@ func (m *memory) Register(_ context.Context, s *register.Service, opts ...regist
 			continue
 		}
 
-		metadata := make(map[string]string, len(n.Metadata))
-
-		// make copy of metadata
-		for k, v := range n.Metadata {
-			metadata[k] = v
-		}
+		md := metadata.Copy(n.Metadata)
 
 		// add the node
 		srvs[s.Name][s.Version].Nodes[n.ID] = &node{
 			Node: &register.Node{
 				ID:       n.ID,
 				Address:  n.Address,
-				Metadata: metadata,
+				Metadata: md,
 			},
 			TTL:      options.TTL,
 			LastSeen: time.Now(),
@@ -452,23 +447,15 @@ func serviceToRecord(s *register.Service, ttl time.Duration) *record {
 }
 
 func recordToService(r *record, namespace string) *register.Service {
-	metadata := make(map[string]string, len(r.Metadata))
-	for k, v := range r.Metadata {
-		metadata[k] = v
-	}
-
 	nodes := make([]*register.Node, len(r.Nodes))
 	i := 0
 	for _, n := range r.Nodes {
-		md := make(map[string]string, len(n.Metadata))
-		for k, v := range n.Metadata {
-			md[k] = v
-		}
+		nmd := metadata.Copy(n.Metadata)
 
 		nodes[i] = &register.Node{
 			ID:       n.ID,
 			Address:  n.Address,
-			Metadata: md,
+			Metadata: nmd,
 		}
 		i++
 	}
diff --git a/register/memory/memory_test.go b/register/memory/memory_test.go
index 348a6c90..71f4cd77 100644
--- a/register/memory/memory_test.go
+++ b/register/memory/memory_test.go
@@ -7,7 +7,7 @@ import (
 	"testing"
 	"time"
 
-	"go.unistack.org/micro/v4/register"
+	"go.unistack.org/micro/v3/register"
 )
 
 var testData = map[string][]*register.Service{
diff --git a/server/registry.go b/server/registry.go
index a6d34fed..9d4bf7dc 100644
--- a/server/registry.go
+++ b/server/registry.go
@@ -77,10 +77,6 @@ func NewRegisterService(s Server) (*register.Service, error) {
 	}
 	node.Metadata = metadata.Copy(opts.Metadata)
 
-	node.Metadata["server"] = s.String()
-	node.Metadata["broker"] = opts.Broker.String()
-	node.Metadata["register"] = opts.Register.String()
-
 	return &register.Service{
 		Name:    opts.Name,
 		Version: opts.Version,