The adjective. Types of adj. Degrees of comparison

Grammatical peculiarities

Modal verbs are also called modal auxiliaries, or modals. Modal verbs are sometimes called defective verbs, because they do not have all the functions of main verbs or auxiliary verbs. They can't be used without a main verb, can't form gerunds or participles, and do not have any endings to show person, number, or tense. Modal verbs form questions without the help of the other auxiliary verbs. Some modal verbs are rarely used in questions. Modal verbs also have quite a few peculiarities in the formation of tenses.

Formation of tenses

Modal verbs do not have the future tense form. The idea of the future is expressed by the present tense forms of modal verbs with the help of the context and adverbs of time referring to the future. (With the exception of the modal verbs WILL, WOULD, of course, which express the future.)
Can I go there tomorrow? - Yes, you can.
Can they go there now? - No, they can't.
He shouldn't call her today.
They should call her tomorrow.
Only two modal verbs can form the past by changing their forms directly. They are CAN - COULD and WILL - WOULD (only in some of their meanings), for example:
She can sing very well. - She could sing very well when she was younger.
He will go there tomorrow. - I said that he would go there tomorrow.
The pair SHALL - SHOULD with the future meaning can still work like that in British English. In American English, WILL is used for all persons in the future (WOULD for the Future in the Past), and SHALL, SHOULD are mostly used as separate modal verbs.
Shall we wait for you here? (polite suggestion of some action and asking for consent or directive)
Shall I bring you more coffee? (polite suggestion of some action and asking for consent or directive)
Should we call her? (asking for advice; present or future)
You should have called her yesterday. (giving advice; past tense)
The verbs MAY and MIGHT are mostly used as separate modal verbs, though MIGHT is generally used instead of MAY in the cases where the rules of the sequence of tenses apply, for example:
She may be at the hospital now. - I said that she might be at the hospital now.