Update guides-metrics.md

docs/guides-metrics.md

@@ -2,4 +2,4 @@
 
 The External Secrets Operator exposes its Prometheus metrics in the `/metrics` path. To enable it, set the `prometheus.enabled` Helm flag to `true`.
 
-The Operator has the metrics inherited from Kubebuilder plus some custom metrics with the `external_secret` prefix.
+The Operator has the metrics inherited from Kubebuilder plus some custom metrics with the `externalsecret` prefix.