A behavior is not exposed as part of metadata.
A behavior can either be a service behavior or an endpoint behavior:
Service Behaviors (behaviors which implement IServiceBehavior
A typical service behavior is the debug logging behavior, which is enabled by adding a serviceBehavior in the config file.
One thing that is important to remember is to associate the service with this behavoir. like this:
<service behaviorConfiguration="ServiceBehavior" name="host.HelloIndigoService">
Behaviors can of cause also be added programmatically.
Endpoint Behaviors(behaviors which implement IEndpointBehavior
A endpoint behavior is defined in the same way, but here its not associate with a service but with the actual endpoint.