The following are modal verbs:
Whether modals, modal verbs, modal auxiliaries or modal auxiliary verbs, they are all the same. The modal verbs and the primary verbs (be, do and have) are called auxiliary verbs. The difference between these two groups of verbs is that we can use modal verbs as auxiliary verbs only. In other words, we cannot use modal verbs on their own in a sentence, as they are not complete by themselves. We have to use them with other verbs, which must be in the simple present tense.
There are 11 modal verbs: can, could, may, might, will, would, shall, should, and must. Words such as had better, ought to, used to, need, and dare are semi-modal verbs as they can function as modal verbs as well as main verbs. Each of the modal verbs is used with another verb to express ideas such as ability, necessity, obligation, permission, possibility, wish, etc. that are not expressed by the main verb. Each one of them can express more than one of these ideas.
- When used with singular or plural subject or noun, the modal verbs do not change their forms: (She will arrive later. / They will arrive later.)
- Modal verbs have no –s form such as when they follow the third person singular subject. (Not: She wills talk to us later. / Not: He shoulds get some rest.)
- Modal verbs do not have present participle form (Not: modal verb + ing).
- Modal verbs do not have past participle form (Not: modal verb + ed).
- Modal verbs do not have infinitive form. They are followed by the infinitive of a simple verb without to (Not: He can to drive a tractor.) There are exceptions: ought to (You ought to be able to read the road sign from here.) and used to (We used to cross that river by ferry.)
- Modal verbs cannot be used with another modal verb. (Not: We can must get it done today.)
- Modal verbs cannot be used on their own in a sentence. They must be followed by other verbs. (No: The repair would one hour. / Yes: The repair would take one hour.)
- Modal verbs can however be used on their own when the main verb is understood. (He could be sleeping. Yes, he could. / She may be angry. Yes, she may.)
- When a modal verb is part of a verb phrase in a sentence, it comes first after the subject and (1) is followed by a main verb in the base form (Subject + modal + basic verb + ... ): She can play the flute. Or (2) is followed by an auxiliary verb (be, do, have): He could be watching television at this time.
Modal verbs always come before the main verb. Both the modal verbs and main verbs are in bold.
Modal verb and contraction
Modal verbs must be placed before the word not or its contraction –n’t (could – couldn’t) in negative sentences. The only modal verb that does not have contraction is may.
Modal verb and adverb