The Node should be labelled with the label k8s-app: metrics-server in order for pods to be scheduled on it.

Check if you have the labels added to the nodes of your cluster: kubectl get nodes --show-labels

And the label should be k8s-app: metrics-server.

apiVersion: v1
kind: Pod
metadata:
  name: testpod
spec:
  containers:
    - name: nginx
      image: nginx:latest
  nodeSelector:
    k8s-app: metrics-server 

Also to check if the pod was scheduled on that node run the following command: kubectl get pods -o wide

Then looking at the “NODE” that the Pod was assigned to.

Following is an excercise again from the kubernetes docs https://kubernetes.io/docs/concepts/scheduling-eviction/assign-pod-node/#nodeselector

Also before you post up a question please try and check online if your question's answer is available. The more you dig, the deeper you will know. Kubernetes docs are too detailed and very easy to understand.