There are ten types of modal verbs: can, could, may, might, will, would, shall, should, must, ought to.
They give additional information about the function of the main verb that comes after it. These are verbs that express different kinds of things. When you use them, they express certainty, necessity, permission, obligation, possibility, etc.. They behave differently from regular verbs:
- Use the modal verb as is and do not change it by using it in present, future, or past forms. You can’t add s, ed, or ing.
- Use the base form of the verb after a modal, without to.
If you use a modal verb in the negative form, include the “not” always after the modal verb.