WHAT ARE MODAL VERBS - Auxiliary verb that expresses necessity or possibility. English modal verbs include must, shall,

Grammar: MODAL VERBS

I should call my sister to find out if she is on her way home.

auxiliary verb that expresses necessity or possibility. English modal verbs include must, shall, will, should, would, can, could, may, and might.

I can walk to the grocery store to buy some milk.

Modals expressing permission: can and may. ...

I could call her if you would like me to.

Modals for likelihood: will, might, may, can, and could. ...

Modals denoting obligation: must and have to. ...

I think you should leave now if you want to catch the train on time.