Modal verbs, sometimes called modals, are auxiliary verbs (helping verbs). They express such things as possibility, probability, permission and obligation.
- Can, could, might, may, must, should, will, would and shall are modal verbs.
Modals are different from normal verbs:
1. Modal verbs do not take "-s" in the third person.
2. You use "not" to make modal verbs negative, even in Simple Present and Simple Past.
3. Many modal verbs cannot be used in the past tenses or the future tenses.
We use a modal verb before a second verb. Modal verbs are not followed by ‘to’.