diff --git a/metadata/context.go b/metadata/context.go
deleted file mode 100644
index e05a37759..000000000
--- a/metadata/context.go
+++ /dev/null
@@ -1,46 +0,0 @@
-package metadata
-
-import (
-	"context"
-	"fmt"
-)
-
-type serverMetadataKey struct{}
-
-// NewServerContext creates a new context with client md attached.
-func NewServerContext(ctx context.Context, md Metadata) context.Context {
-	return context.WithValue(ctx, serverMetadataKey{}, md)
-}
-
-// FromServerContext returns the server metadata in ctx if it exists.
-func FromServerContext(ctx context.Context) (Metadata, bool) {
-	md, ok := ctx.Value(serverMetadataKey{}).(Metadata)
-	return md, ok
-}
-
-type clientMetadataKey struct{}
-
-// NewClientContext creates a new context with client md attached.
-func NewClientContext(ctx context.Context, md Metadata) context.Context {
-	return context.WithValue(ctx, clientMetadataKey{}, md)
-}
-
-// FromClientContext returns the client metadata in ctx if it exists.
-func FromClientContext(ctx context.Context) (Metadata, bool) {
-	md, ok := ctx.Value(clientMetadataKey{}).(Metadata)
-	return md, ok
-}
-
-// AppendToClientContext returns a new context with the provided kv merged
-// with any existing metadata in the context.
-func AppendToClientContext(ctx context.Context, kv ...string) context.Context {
-	if len(kv)%2 == 1 {
-		panic(fmt.Sprintf("metadata: AppendToOutgoingContext got an odd number of input pairs for metadata: %d", len(kv)))
-	}
-	md, _ := FromClientContext(ctx)
-	md = md.Clone()
-	for i := 0; i < len(kv); i += 2 {
-		md.Set(kv[i], kv[i+1])
-	}
-	return NewClientContext(ctx, md)
-}
diff --git a/metadata/metadata.go b/metadata/metadata.go
index 7cc225f24..21b7547db 100644
--- a/metadata/metadata.go
+++ b/metadata/metadata.go
@@ -1,6 +1,8 @@
 package metadata
 
 import (
+	"context"
+	"fmt"
 	"strings"
 )
 
@@ -41,6 +43,16 @@ func (m Metadata) Set(key string, value string) {
 	m[k] = value
 }
 
+// Range iterate over element in metadata.
+func (m Metadata) Range(f func(k, v string) bool) {
+	for k, v := range m {
+		ret := f(k, v)
+		if ret == false {
+			break
+		}
+	}
+}
+
 // Clone returns a deep copy of Metadata
 func (m Metadata) Clone() Metadata {
 	md := Metadata{}
@@ -49,3 +61,53 @@ func (m Metadata) Clone() Metadata {
 	}
 	return md
 }
+
+type serverMetadataKey struct{}
+
+// NewServerContext creates a new context with client md attached.
+func NewServerContext(ctx context.Context, md Metadata) context.Context {
+	return context.WithValue(ctx, serverMetadataKey{}, md)
+}
+
+// FromServerContext returns the server metadata in ctx if it exists.
+func FromServerContext(ctx context.Context) (Metadata, bool) {
+	md, ok := ctx.Value(serverMetadataKey{}).(Metadata)
+	return md, ok
+}
+
+type clientMetadataKey struct{}
+
+// NewClientContext creates a new context with client md attached.
+func NewClientContext(ctx context.Context, md Metadata) context.Context {
+	return context.WithValue(ctx, clientMetadataKey{}, md)
+}
+
+// FromClientContext returns the client metadata in ctx if it exists.
+func FromClientContext(ctx context.Context) (Metadata, bool) {
+	md, ok := ctx.Value(clientMetadataKey{}).(Metadata)
+	return md, ok
+}
+
+// AppendToClientContext returns a new context with the provided kv merged
+// with any existing metadata in the context.
+func AppendToClientContext(ctx context.Context, kv ...string) context.Context {
+	if len(kv)%2 == 1 {
+		panic(fmt.Sprintf("metadata: AppendToOutgoingContext got an odd number of input pairs for metadata: %d", len(kv)))
+	}
+	md, _ := FromClientContext(ctx)
+	md = md.Clone()
+	for i := 0; i < len(kv); i += 2 {
+		md.Set(kv[i], kv[i+1])
+	}
+	return NewClientContext(ctx, md)
+}
+
+// MergeToClientContext merge new metadata into ctx.
+func MergeToClientContext(ctx context.Context, cmd Metadata) context.Context {
+	md, _ := FromClientContext(ctx)
+	md = md.Clone()
+	for k, v := range cmd {
+		md[k] = v
+	}
+	return NewClientContext(ctx, md)
+}
diff --git a/middleware/metadata/metadata.go b/middleware/metadata/metadata.go
index ac1e76ed0..aaa566743 100644
--- a/middleware/metadata/metadata.go
+++ b/middleware/metadata/metadata.go
@@ -17,24 +17,24 @@ type options struct {
 	md     metadata.Metadata
 }
 
-// WithConstants is option with constant metadata key value.
+// WithConstants with constant metadata key value.
 func WithConstants(md metadata.Metadata) Option {
 	return func(o *options) {
 		o.md = md
 	}
 }
 
-// WithPropagatedPrefix is option with global propagated key prefix.
+// WithPropagatedPrefix with propagated key prefix.
 func WithPropagatedPrefix(prefix ...string) Option {
 	return func(o *options) {
 		o.prefix = prefix
 	}
 }
 
-// Server is middleware client-side metadata.
+// Server is middleware server-side metadata.
 func Server(opts ...Option) middleware.Middleware {
 	options := options{
-		prefix: []string{"x-md-global-", "x-md-local-"},
+		prefix: []string{"x-md-"}, // x-md-global-, x-md-local
 	}
 	for _, o := range opts {
 		o(&options)
@@ -42,11 +42,10 @@ func Server(opts ...Option) middleware.Middleware {
 	return func(handler middleware.Handler) middleware.Handler {
 		return func(ctx context.Context, req interface{}) (reply interface{}, err error) {
 			if tr, ok := transport.FromServerContext(ctx); ok {
-				md := metadata.Metadata{}
+				md := metadata.New()
 				for _, k := range tr.Header().Keys() {
-					key := strings.ToLower(k)
 					for _, prefix := range options.prefix {
-						if strings.HasPrefix(key, prefix) {
+						if strings.HasPrefix(strings.ToLower(k), prefix) {
 							md.Set(k, tr.Header().Get(k))
 							break
 						}
@@ -70,6 +69,7 @@ func Client(opts ...Option) middleware.Middleware {
 	return func(handler middleware.Handler) middleware.Handler {
 		return func(ctx context.Context, req interface{}) (reply interface{}, err error) {
 			if tr, ok := transport.FromClientContext(ctx); ok {
+				// x-md-local-
 				for k, v := range options.md {
 					tr.Header().Set(k, v)
 				}
@@ -78,6 +78,7 @@ func Client(opts ...Option) middleware.Middleware {
 						tr.Header().Set(k, v)
 					}
 				}
+				// x-md-global-
 				if md, ok := metadata.FromServerContext(ctx); ok {
 					for k, v := range md {
 						for _, prefix := range options.prefix {