The metrics server is important for the HorizontalPodAutoscaler to work. Observability is not related to it.
helm repo add metrics-server \
https://kubernetes-sigs.github.io/metrics-server/
helm repo update
# Note that this deployment skips tls verification
# and is not suited for productive use
helm upgrade -n kube-system \
--install --atomic --wait \
--set args[0]=--kubelet-insecure-tls \
metrics-server metrics-server/metrics-server