diff --git a/auth/auth.go b/auth/auth.go
index 4559f69d..cbd587b8 100644
--- a/auth/auth.go
+++ b/auth/auth.go
@@ -5,6 +5,8 @@ import (
 	"context"
 	"errors"
 	"time"
+
+	"github.com/unistack-org/micro/v3/metadata"
 )
 
 const (
@@ -57,7 +59,7 @@ type Account struct {
 	// Issuer of the account
 	Issuer string `json:"issuer"`
 	// Any other associated metadata
-	Metadata map[string]string `json:"metadata"`
+	Metadata metadata.Metadata `json:"metadata"`
 	// Scopes the account has access to
 	Scopes []string `json:"scopes"`
 	// Secret for the account, e.g. the password
diff --git a/auth/options.go b/auth/options.go
index fd77d72e..225c5194 100644
--- a/auth/options.go
+++ b/auth/options.go
@@ -5,6 +5,7 @@ import (
 	"time"
 
 	"github.com/unistack-org/micro/v3/logger"
+	"github.com/unistack-org/micro/v3/metadata"
 	"github.com/unistack-org/micro/v3/store"
 )
 
@@ -102,7 +103,7 @@ func LoginURL(url string) Option {
 
 type GenerateOptions struct {
 	// Metadata associated with the account
-	Metadata map[string]string
+	Metadata metadata.Metadata
 	// Scopes the account has access too
 	Scopes []string
 	// Provider of the account, e.g. oauth
@@ -132,9 +133,9 @@ func WithType(t string) GenerateOption {
 }
 
 // WithMetadata for the generated account
-func WithMetadata(md map[string]string) GenerateOption {
+func WithMetadata(md metadata.Metadata) GenerateOption {
 	return func(o *GenerateOptions) {
-		o.Metadata = md
+		o.Metadata = metadata.Copy(md)
 	}
 }
 
diff --git a/broker/broker.go b/broker/broker.go
index 62e7cfd7..2a68d9b8 100644
--- a/broker/broker.go
+++ b/broker/broker.go
@@ -1,7 +1,11 @@
 // Package broker is an interface used for asynchronous messaging
 package broker
 
-import "context"
+import (
+	"context"
+
+	"github.com/unistack-org/micro/v3/metadata"
+)
 
 var (
 	DefaultBroker Broker = NewBroker()
@@ -32,7 +36,7 @@ type Event interface {
 
 // Message is used to transfer data
 type Message struct {
-	Header map[string]string // contains message metadata
+	Header metadata.Metadata // contains message metadata
 	Body   []byte            // contains message body
 }
 
diff --git a/client/client.go b/client/client.go
index b74ed654..b89f6e0f 100644
--- a/client/client.go
+++ b/client/client.go
@@ -6,6 +6,7 @@ import (
 	"time"
 
 	"github.com/unistack-org/micro/v3/codec"
+	"github.com/unistack-org/micro/v3/metadata"
 )
 
 var (
@@ -57,7 +58,7 @@ type Response interface {
 	// Read the response
 	Codec() codec.Reader
 	// read the header
-	Header() map[string]string
+	Header() metadata.Metadata
 	// Read the undecoded response
 	Read() ([]byte, error)
 }
diff --git a/client/noop.go b/client/noop.go
index 59bd5d42..b9e99d19 100644
--- a/client/noop.go
+++ b/client/noop.go
@@ -66,14 +66,14 @@ func (n *noopRequest) Stream() bool {
 
 type noopResponse struct {
 	codec  codec.Reader
-	header map[string]string
+	header metadata.Metadata
 }
 
 func (n *noopResponse) Codec() codec.Reader {
 	return n.codec
 }
 
-func (n *noopResponse) Header() map[string]string {
+func (n *noopResponse) Header() metadata.Metadata {
 	return n.header
 }
 
diff --git a/codec/codec.go b/codec/codec.go
index e1685f9e..554969d2 100644
--- a/codec/codec.go
+++ b/codec/codec.go
@@ -4,6 +4,8 @@ package codec
 import (
 	"errors"
 	"io"
+
+	"github.com/unistack-org/micro/v3/metadata"
 )
 
 const (
@@ -67,6 +69,6 @@ type Message struct {
 	Error    string
 
 	// The values read from the socket
-	Header map[string]string
+	Header metadata.Metadata
 	Body   []byte
 }
diff --git a/debug/log/kubernetes/kubernetes.go b/debug/log/kubernetes/kubernetes.go
index 9ae75121..9fc17b10 100644
--- a/debug/log/kubernetes/kubernetes.go
+++ b/debug/log/kubernetes/kubernetes.go
@@ -11,6 +11,7 @@ import (
 	"time"
 
 	"github.com/unistack-org/micro/v3/debug/log"
+	"github.com/unistack-org/micro/v3/metadata"
 	"github.com/unistack-org/micro/v3/util/kubernetes/client"
 )
 
@@ -89,7 +90,7 @@ func (k *klog) parse(line string) log.Record {
 	if err := json.Unmarshal([]byte(line), &record); err != nil {
 		record.Timestamp = time.Now().UTC()
 		record.Message = line
-		record.Metadata = make(map[string]string)
+		record.Metadata = metadata.New(1)
 	}
 
 	record.Metadata["service"] = k.Options.Name
diff --git a/debug/log/log.go b/debug/log/log.go
index dabdb899..4bff048d 100644
--- a/debug/log/log.go
+++ b/debug/log/log.go
@@ -5,6 +5,8 @@ import (
 	"encoding/json"
 	"fmt"
 	"time"
+
+	"github.com/unistack-org/micro/v3/metadata"
 )
 
 var (
@@ -29,7 +31,7 @@ type Record struct {
 	// Timestamp of logged event
 	Timestamp time.Time `json:"timestamp"`
 	// Metadata to enrich log record
-	Metadata map[string]string `json:"metadata"`
+	Metadata metadata.Metadata `json:"metadata"`
 	// Value contains log entry
 	Message interface{} `json:"message"`
 }
diff --git a/events/events.go b/events/events.go
index 4d0ffa45..da0f1a11 100644
--- a/events/events.go
+++ b/events/events.go
@@ -6,6 +6,8 @@ import (
 	"encoding/json"
 	"errors"
 	"time"
+
+	"github.com/unistack-org/micro/v3/metadata"
 )
 
 var (
@@ -36,7 +38,7 @@ type Event struct {
 	// Timestamp of the event
 	Timestamp time.Time
 	// Metadata contains the encoded event was indexed by
-	Metadata map[string]string
+	Metadata metadata.Metadata
 	// Payload contains the encoded message
 	Payload []byte
 }
diff --git a/events/options.go b/events/options.go
index f9314528..4a14a9e5 100644
--- a/events/options.go
+++ b/events/options.go
@@ -1,11 +1,15 @@
 package events
 
-import "time"
+import (
+	"time"
+
+	"github.com/unistack-org/micro/v3/metadata"
+)
 
 // PublishOptions contains all the options which can be provided when publishing an event
 type PublishOptions struct {
 	// Metadata contains any keys which can be used to query the data, for example a customer id
-	Metadata map[string]string
+	Metadata metadata.Metadata
 	// Timestamp to set for the event, if the timestamp is a zero value, the current time will be used
 	Timestamp time.Time
 }
@@ -14,9 +18,9 @@ type PublishOptions struct {
 type PublishOption func(o *PublishOptions)
 
 // WithMetadata sets the Metadata field on PublishOptions
-func WithMetadata(md map[string]string) PublishOption {
+func WithMetadata(md metadata.Metadata) PublishOption {
 	return func(o *PublishOptions) {
-		o.Metadata = md
+		o.Metadata = metadata.Copy(md)
 	}
 }
 
diff --git a/metrics/noop.go b/metrics/noop.go
index ffb4e143..d93b1483 100644
--- a/metrics/noop.go
+++ b/metrics/noop.go
@@ -2,6 +2,8 @@ package metrics
 
 import (
 	"time"
+
+	"github.com/unistack-org/micro/v3/metadata"
 )
 
 // NoopReporter is an noop implementation of Reporter:
@@ -25,17 +27,17 @@ func (r *noopReporter) Init(opts ...Option) error {
 }
 
 // Count implements the Reporter interface Count method:
-func (r *noopReporter) Count(metricName string, value int64, tags Tags) error {
+func (r *noopReporter) Count(metricName string, value int64, md metadata.Metadata) error {
 	return nil
 }
 
 // Gauge implements the Reporter interface Gauge method:
-func (r *noopReporter) Gauge(metricName string, value float64, tags Tags) error {
+func (r *noopReporter) Gauge(metricName string, value float64, md metadata.Metadata) error {
 	return nil
 }
 
 // Timing implements the Reporter interface Timing method:
-func (r *noopReporter) Timing(metricName string, value time.Duration, tags Tags) error {
+func (r *noopReporter) Timing(metricName string, value time.Duration, md metadata.Metadata) error {
 	return nil
 }
 
diff --git a/metrics/options.go b/metrics/options.go
index a38e183f..1b285ebf 100644
--- a/metrics/options.go
+++ b/metrics/options.go
@@ -1,6 +1,9 @@
 package metrics
 
-import "github.com/unistack-org/micro/v3/logger"
+import (
+	"github.com/unistack-org/micro/v3/logger"
+	"github.com/unistack-org/micro/v3/metadata"
+)
 
 var (
 	// The Prometheus metrics will be made available on this port:
@@ -18,7 +21,7 @@ type Option func(*Options)
 type Options struct {
 	Address          string
 	Path             string
-	DefaultTags      Tags
+	DefaultTags      metadata.Metadata
 	TimingObjectives map[float64]float64
 	Logger           logger.Logger
 }
@@ -27,7 +30,7 @@ type Options struct {
 func NewOptions(opt ...Option) Options {
 	opts := Options{
 		Address:          defaultPrometheusListenAddress,
-		DefaultTags:      make(Tags),
+		DefaultTags:      metadata.New(2),
 		Path:             defaultPath,
 		TimingObjectives: defaultTimingObjectives,
 	}
@@ -54,9 +57,9 @@ func Address(value string) Option {
 }
 
 // DefaultTags will be added to every metric:
-func DefaultTags(value Tags) Option {
+func DefaultTags(md metadata.Metadata) Option {
 	return func(o *Options) {
-		o.DefaultTags = value
+		o.DefaultTags = metadata.Copy(md)
 	}
 }
 
diff --git a/metrics/reporter.go b/metrics/reporter.go
index b0e45197..4a2ca1c5 100644
--- a/metrics/reporter.go
+++ b/metrics/reporter.go
@@ -1,10 +1,11 @@
 // Package metrics is for instrumentation and debugging
 package metrics
 
-import "time"
+import (
+	"time"
 
-// Tags is a map of fields to add to a metric:
-type Tags map[string]string
+	"github.com/unistack-org/micro/v3/metadata"
+)
 
 var (
 	DefaultReporter Reporter = NewReporter()
@@ -13,8 +14,8 @@ var (
 // Reporter is an interface for collecting and instrumenting metrics
 type Reporter interface {
 	Init(...Option) error
-	Count(id string, value int64, tags Tags) error
-	Gauge(id string, value float64, tags Tags) error
-	Timing(id string, value time.Duration, tags Tags) error
+	Count(id string, value int64, md metadata.Metadata) error
+	Gauge(id string, value float64, md metadata.Metadata) error
+	Timing(id string, value time.Duration, md metadata.Metadata) error
 	Options() Options
 }
diff --git a/metrics/wrapper/metrics_wrapper.go b/metrics/wrapper/metrics_wrapper.go
index be4a6922..2b7b2fe6 100644
--- a/metrics/wrapper/metrics_wrapper.go
+++ b/metrics/wrapper/metrics_wrapper.go
@@ -1,10 +1,10 @@
 package wrapper
 
 import (
+	"context"
 	"time"
 
-	"context"
-
+	"github.com/unistack-org/micro/v3/metadata"
 	"github.com/unistack-org/micro/v3/metrics"
 	"github.com/unistack-org/micro/v3/server"
 )
@@ -26,9 +26,8 @@ func (w *Wrapper) HandlerFunc(handlerFunction server.HandlerFunc) server.Handler
 	return func(ctx context.Context, req server.Request, rsp interface{}) error {
 
 		// Build some tags to describe the call:
-		tags := metrics.Tags{
-			"method": req.Method(),
-		}
+		tags := metadata.New(2)
+		tags.Set("method", req.Method())
 
 		// Start the clock:
 		callTime := time.Now()
diff --git a/network/transport/transport.go b/network/transport/transport.go
index 0cfe0b21..cd3e8a58 100644
--- a/network/transport/transport.go
+++ b/network/transport/transport.go
@@ -4,6 +4,8 @@ package transport
 import (
 	"context"
 	"time"
+
+	"github.com/unistack-org/micro/v3/metadata"
 )
 
 var (
@@ -26,7 +28,7 @@ type Transport interface {
 
 // Message is used to transfer data
 type Message struct {
-	Header map[string]string
+	Header metadata.Metadata
 	Body   []byte
 }
 
diff --git a/options.go b/options.go
index 2c6012e6..446dcad0 100644
--- a/options.go
+++ b/options.go
@@ -12,6 +12,7 @@ import (
 	"github.com/unistack-org/micro/v3/config"
 	"github.com/unistack-org/micro/v3/debug/profile"
 	"github.com/unistack-org/micro/v3/logger"
+	"github.com/unistack-org/micro/v3/metadata"
 	"github.com/unistack-org/micro/v3/network/transport"
 	"github.com/unistack-org/micro/v3/registry"
 	"github.com/unistack-org/micro/v3/router"
@@ -260,7 +261,7 @@ func Version(v string) Option {
 }
 
 // Metadata associated with the service
-func Metadata(md map[string]string) Option {
+func Metadata(md metadata.Metadata) Option {
 	return func(o *Options) {
 		if o.Server != nil {
 			o.Server.Init(server.Metadata(md))
diff --git a/registry/extractor.go b/registry/extractor.go
index 602eb615..038d4c48 100644
--- a/registry/extractor.go
+++ b/registry/extractor.go
@@ -100,9 +100,7 @@ func ExtractEndpoint(method reflect.Method) *Endpoint {
 	}
 
 	if stream {
-		ep.Metadata = map[string]string{
-			"stream": fmt.Sprintf("%v", stream),
-		}
+		ep.Metadata.Set("stream", fmt.Sprintf("%v", stream))
 	}
 
 	return ep
diff --git a/registry/registry.go b/registry/registry.go
index 3898d926..70dc4e49 100644
--- a/registry/registry.go
+++ b/registry/registry.go
@@ -4,6 +4,8 @@ package registry
 import (
 	"context"
 	"errors"
+
+	"github.com/unistack-org/micro/v3/metadata"
 )
 
 const (
@@ -42,7 +44,7 @@ type Registry interface {
 type Service struct {
 	Name      string            `json:"name"`
 	Version   string            `json:"version"`
-	Metadata  map[string]string `json:"metadata"`
+	Metadata  metadata.Metadata `json:"metadata"`
 	Endpoints []*Endpoint       `json:"endpoints"`
 	Nodes     []*Node           `json:"nodes"`
 }
@@ -51,7 +53,7 @@ type Service struct {
 type Node struct {
 	Id       string            `json:"id"`
 	Address  string            `json:"address"`
-	Metadata map[string]string `json:"metadata"`
+	Metadata metadata.Metadata `json:"metadata"`
 }
 
 // Endpoint holds endpoint registry info
@@ -59,7 +61,7 @@ type Endpoint struct {
 	Name     string            `json:"name"`
 	Request  *Value            `json:"request"`
 	Response *Value            `json:"response"`
-	Metadata map[string]string `json:"metadata"`
+	Metadata metadata.Metadata `json:"metadata"`
 }
 
 // Valud holds additional kv stuff
diff --git a/router/route.go b/router/route.go
index 9d844885..50d535a8 100644
--- a/router/route.go
+++ b/router/route.go
@@ -2,6 +2,8 @@ package router
 
 import (
 	"hash/fnv"
+
+	"github.com/unistack-org/micro/v3/metadata"
 )
 
 var (
@@ -28,7 +30,7 @@ type Route struct {
 	// Metric is the route cost metric
 	Metric int64
 	// Metadata for the route
-	Metadata map[string]string
+	Metadata metadata.Metadata
 }
 
 // Hash returns route hash sum.
diff --git a/runtime/runtime.go b/runtime/runtime.go
index f46a9aab..87921314 100644
--- a/runtime/runtime.go
+++ b/runtime/runtime.go
@@ -4,6 +4,8 @@ package runtime
 import (
 	"errors"
 	"time"
+
+	"github.com/unistack-org/micro/v3/metadata"
 )
 
 var (
@@ -43,7 +45,7 @@ type Logs interface {
 // Log is a log message
 type Log struct {
 	Message  string
-	Metadata map[string]string
+	Metadata metadata.Metadata
 }
 
 // Scheduler is a runtime service scheduler
@@ -103,7 +105,7 @@ type Service struct {
 	// url location of source
 	Source string
 	// Metadata stores metadata
-	Metadata map[string]string
+	Metadata metadata.Metadata
 }
 
 // Resources which are allocated to a serivce
diff --git a/server/options.go b/server/options.go
index 2d96ac5b..d165918a 100644
--- a/server/options.go
+++ b/server/options.go
@@ -10,6 +10,7 @@ import (
 	"github.com/unistack-org/micro/v3/broker"
 	"github.com/unistack-org/micro/v3/codec"
 	"github.com/unistack-org/micro/v3/logger"
+	"github.com/unistack-org/micro/v3/metadata"
 	"github.com/unistack-org/micro/v3/network/transport"
 	"github.com/unistack-org/micro/v3/registry"
 	"github.com/unistack-org/micro/v3/tracer"
@@ -24,7 +25,7 @@ type Options struct {
 	Auth         auth.Auth
 	Logger       logger.Logger
 	Transport    transport.Transport
-	Metadata     map[string]string
+	Metadata     metadata.Metadata
 	Name         string
 	Address      string
 	Advertise    string
@@ -63,7 +64,7 @@ func NewOptions(opts ...Option) Options {
 		Auth:             auth.DefaultAuth,
 		Codecs:           make(map[string]codec.NewCodec),
 		Context:          context.Background(),
-		Metadata:         map[string]string{},
+		Metadata:         metadata.New(0),
 		RegisterInterval: DefaultRegisterInterval,
 		RegisterTTL:      DefaultRegisterTTL,
 		RegisterCheck:    DefaultRegisterCheck,
@@ -187,9 +188,9 @@ func Transport(t transport.Transport) Option {
 }
 
 // Metadata associated with the server
-func Metadata(md map[string]string) Option {
+func Metadata(md metadata.Metadata) Option {
 	return func(o *Options) {
-		o.Metadata = md
+		o.Metadata = metadata.Copy(md)
 	}
 }
 
@@ -271,7 +272,7 @@ type HandlerOption func(*HandlerOptions)
 // HandlerOptions struct
 type HandlerOptions struct {
 	Internal bool
-	Metadata map[string]map[string]string
+	Metadata map[string]metadata.Metadata
 	Context  context.Context
 }
 
@@ -317,9 +318,9 @@ func NewSubscriberOptions(opts ...SubscriberOption) SubscriberOptions {
 
 // EndpointMetadata is a Handler option that allows metadata to be added to
 // individual endpoints.
-func EndpointMetadata(name string, md map[string]string) HandlerOption {
+func EndpointMetadata(name string, md metadata.Metadata) HandlerOption {
 	return func(o *HandlerOptions) {
-		o.Metadata[name] = md
+		o.Metadata[name] = metadata.Copy(md)
 	}
 }
 
diff --git a/server/request.go b/server/request.go
index 1cde9feb..f4496482 100644
--- a/server/request.go
+++ b/server/request.go
@@ -2,13 +2,14 @@ package server
 
 import (
 	"github.com/unistack-org/micro/v3/codec"
+	"github.com/unistack-org/micro/v3/metadata"
 )
 
 type rpcMessage struct {
 	topic       string
 	contentType string
 	payload     interface{}
-	header      map[string]string
+	header      metadata.Metadata
 	body        []byte
 	codec       codec.Codec
 }
@@ -25,7 +26,7 @@ func (r *rpcMessage) Payload() interface{} {
 	return r.payload
 }
 
-func (r *rpcMessage) Header() map[string]string {
+func (r *rpcMessage) Header() metadata.Metadata {
 	return r.header
 }
 
diff --git a/server/server.go b/server/server.go
index 9ceba30a..802390b0 100644
--- a/server/server.go
+++ b/server/server.go
@@ -7,6 +7,7 @@ import (
 
 	"github.com/google/uuid"
 	"github.com/unistack-org/micro/v3/codec"
+	"github.com/unistack-org/micro/v3/metadata"
 	"github.com/unistack-org/micro/v3/registry"
 )
 
@@ -53,7 +54,7 @@ type Message interface {
 	// The content type of the payload
 	ContentType() string
 	// The raw headers of the message
-	Header() map[string]string
+	Header() metadata.Metadata
 	// The raw body of the message
 	Body() []byte
 	// Codec used to decode the message
@@ -71,7 +72,7 @@ type Request interface {
 	// Content type provided
 	ContentType() string
 	// Header of the request
-	Header() map[string]string
+	Header() metadata.Metadata
 	// Body is the initial decoded value
 	Body() interface{}
 	// Read the undecoded request body
@@ -87,7 +88,7 @@ type Response interface {
 	// Encoded writer
 	Codec() codec.Writer
 	// Write the header
-	WriteHeader(map[string]string)
+	WriteHeader(metadata.Metadata)
 	// write a response directly to the client
 	Write([]byte) error
 }
diff --git a/server/subscriber.go b/server/subscriber.go
index 87e7c899..21ec7d14 100644
--- a/server/subscriber.go
+++ b/server/subscriber.go
@@ -134,15 +134,14 @@ func newSubscriber(topic string, sub interface{}, opts ...SubscriberOption) Subs
 		}
 
 		handlers = append(handlers, h)
-
-		endpoints = append(endpoints, &registry.Endpoint{
-			Name:    "Func",
-			Request: registry.ExtractSubValue(typ),
-			Metadata: map[string]string{
-				"topic":      topic,
-				"subscriber": "true",
-			},
-		})
+		ep := &registry.Endpoint{
+			Name:     "Func",
+			Request:  registry.ExtractSubValue(typ),
+			Metadata: metadata.New(2),
+		}
+		ep.Metadata.Set("topic", topic)
+		ep.Metadata.Set("subscriber", "true")
+		endpoints = append(endpoints, ep)
 	} else {
 		hdlr := reflect.ValueOf(sub)
 		name := reflect.Indirect(hdlr).Type().Name()
@@ -162,15 +161,14 @@ func newSubscriber(topic string, sub interface{}, opts ...SubscriberOption) Subs
 			}
 
 			handlers = append(handlers, h)
-
-			endpoints = append(endpoints, &registry.Endpoint{
-				Name:    name + "." + method.Name,
-				Request: registry.ExtractSubValue(method.Type),
-				Metadata: map[string]string{
-					"topic":      topic,
-					"subscriber": "true",
-				},
-			})
+			ep := &registry.Endpoint{
+				Name:     name + "." + method.Name,
+				Request:  registry.ExtractSubValue(method.Type),
+				Metadata: metadata.New(2),
+			}
+			ep.Metadata.Set("topic", topic)
+			ep.Metadata.Set("subscriber", "true")
+			endpoints = append(endpoints, ep)
 		}
 	}
 
diff --git a/tracer/context.go b/tracer/context.go
index a2fd4372..8bbaab66 100644
--- a/tracer/context.go
+++ b/tracer/context.go
@@ -29,8 +29,8 @@ func FromContext(ctx context.Context) (traceID string, parentSpanID string, isFo
 
 // NewContext saves the trace and span ids in the context
 func NewContext(ctx context.Context, traceID, parentSpanID string) context.Context {
-	return metadata.MergeContext(ctx, map[string]string{
-		traceIDKey: traceID,
-		spanIDKey:  parentSpanID,
-	}, true)
+	md := metadata.New(2)
+	md.Set(traceIDKey, traceID)
+	md.Set(spanIDKey, parentSpanID)
+	return metadata.MergeContext(ctx, md, true)
 }
diff --git a/tracer/trace.go b/tracer/trace.go
index f4bb1b35..434843cb 100644
--- a/tracer/trace.go
+++ b/tracer/trace.go
@@ -4,6 +4,8 @@ package tracer
 import (
 	"context"
 	"time"
+
+	"github.com/unistack-org/micro/v3/metadata"
 )
 
 var (
@@ -46,7 +48,7 @@ type Span struct {
 	// Duration in nano seconds
 	Duration time.Duration
 	// associated data
-	Metadata map[string]string
+	Metadata metadata.Metadata
 	// Type
 	Type SpanType
 }
diff --git a/util/stream/stream.go b/util/stream/stream.go
index af5f8b8d..158d1450 100644
--- a/util/stream/stream.go
+++ b/util/stream/stream.go
@@ -35,7 +35,7 @@ func (r *request) Codec() codec.Reader {
 	return r.Request.Codec().(codec.Reader)
 }
 
-func (r *request) Header() map[string]string {
+func (r *request) Header() metadata.Metadata {
 	md, _ := metadata.FromContext(r.context)
 	return md
 }
diff --git a/util/token/jwt/jwt.go b/util/token/jwt/jwt.go
index c621055a..cbc3f989 100644
--- a/util/token/jwt/jwt.go
+++ b/util/token/jwt/jwt.go
@@ -6,6 +6,7 @@ import (
 
 	"github.com/dgrijalva/jwt-go"
 	"github.com/unistack-org/micro/v3/auth"
+	"github.com/unistack-org/micro/v3/metadata"
 	"github.com/unistack-org/micro/v3/util/token"
 )
 
@@ -13,7 +14,7 @@ import (
 type authClaims struct {
 	Type     string            `json:"type"`
 	Scopes   []string          `json:"scopes"`
-	Metadata map[string]string `json:"metadata"`
+	Metadata metadata.Metadata `json:"metadata"`
 
 	jwt.StandardClaims
 }