Hi Patrick,
which part of registering Metrics do you need help with?
If you already have your metrics, check out https://docs.spring.io/spring-boot/docs/current/reference/html/production-ready-metrics.html#production-ready-dropwizard-metrics to see how to register them with Spring Boot.
To register the metrics measurements in Axon, check out the axon-metrics component. It contains a “org.axonframework.metrics.GlobalMetricRegistry” class that allows you to register metrics implementations of MessageMonitors for your components. If you autowire your (Axon) Configurer, MetricsRegistry (the one from dropwizard), you can instantiate a GlobalMetricRegistry instance and tell it to configure the Configurer to use the Metrics implementations. Tip: you can use @Autowired methods in your Spring Configuration classes to do these kind of things easily.
Cheers,
Allard