The Elastic Stack monitoring features consist of two components: an agent that you install on each Elasticsearch and Logstash node, and a Monitoring UI in Kibana. The monitoring agent collects and indexes metrics from the nodes and you visualize the data through the Monitoring dashboards in Kibana. The agent can index data on the same Elasticsearch cluster, or send it to an external monitoring cluster.
To use the monitoring features with the security features enabled, you need to set up Kibana to work with the security features and create at least one user for the Monitoring UI. If you are using an external monitoring cluster, you also need to configure a user for the monitoring agent and configure the agent to use the appropriate credentials when communicating with the monitoring cluster.
For more information, see:
Intro to Kibana
ELK for Logs & Metrics