Prometheus Operator is the perfect cloud-native monitoring solution for Kubernetes. By deploying the Helm chart you get a preconfigured Prometheus and Grafana setup plus an array of CRDs to add monitoring your own services.
Not everything necessarily lives in a Kubernetes cluster, though. So how would you add external targets to a Prometheus Operator setup? One could define an Endpoint, Service and ServiceMonitor for the external resource to have it picked up by Prometheus' Kubernetes service discovery, which works, but there is a better solution that is more in line with how Prometheus is used outside of the Operator deployment.