Here is a list of the modal verbs.

       CAN           COULD       MAY        MIGHT          WILL

    

     WOULD        MUST       SHALL     SHOULD       OUGHT TO       

     

We use  CAN and COULD  to talk about a skill or ability.

 ex: I CAN speak seven languages.

       My son COULD play golf very well.

We can use verbs such as MUST OR SHOULD to say when something is necessary or unnecessary or to give advice.

ex: Children MUST do their homework.

     You SHOULD stop smoking.