Be, do, and have also differ from the other auxiliaries in that they can also serve as ordinary verbs in a given sentence.
The modal verbs are:-
CAN / COULD / MAY / MIGHT / MUST / SHALL / SHOULD / OUGHT TO / WILL / WOULD
!Note The modal auxiliary verbs are always followed by the base form. The verb used to, which is explained here, can also be used like a modal verb.