The current JMX export for metrics is using the default DropWizard metrics API domain (which is 'metrics').
When connecting to a Jenkins instance using JMX, it is not obvious at all that the domain 'metrics' is in fact hosting Jenkins metrics.
JMX best practices
The domain part of an Object Name should start with a Java package name. This prevents collisions between MBeans coming from different subsystems. There might be additional text after the package name. Examples:
Therefore, I propose to use io.jenkins as domain to expose metrics via JMX.