USES OF MODALS OR SEMI-AUXILIARIES.
Modals accompany(HELP) the main verbs to enforce meaning: permission/no permission, suggestion, obligation etc, for the verb to be executed and also express tense,
Examples: Can, could, may, might, should, ought to, must, will, would. (need to, have to)
* They are always followed by mostly the bare infinitive (without ‘to’). I can do, I may come, we should go, you ought to visit us.
*They have the same form for all the pronouns during conjugation: I should, You should, He should, we should.
*They take direct negative and question forms: can/can’t, should, shouldn’t, except for ‘may’ which does not receive the contracted form in the negative – ‘may not’, ‘*may’nt’. Can we? , may we? etc, goes for the direct question form.
*Modals never combine with another modal: you may can.
NB: Although ‘have to’ and ‘need to‘, have some aspects of the formulation of the modals; like being followed by the bare infinitive, they are not modal verbs. They change form with persons (I,you,He, we, they)
Some uses of the modals
1: Ability/lack of ability: can and could /Dogs can bark for the whole day./ We could drive long distances in the past.
2. Informal request: Can you turn the music down, please?
3. General possibility: Prices could rise.
4: Polite request: Could we move on, please? A Polite modal verb is used to ask permission: May(there is no contracted form), might. May I borrow your pen?
5. Expressing an opinion, an expectation, giving advice: /We should have a rest/His son is sick. I think we should pay him a visit./ We should consume less sugar/
6. ‘Should‘ can replace if– in the conditional sentence: Should there be any complaints, hint me.
7. Expressing necessity, obligation ‘Must’,’have to’, ‘ought to’, ‘need to’- I am feeling tired. I must have a rest./ I ought to/ have to be up before 6:00AM.
8. Expressing the future simple tense: SHALL only for I and we), WILL :/ I/we shall go to school tomorrow./He will arrive in the morning/.
9. Formulation of conditional sentences: Will, Would: / If I am sick I will go home/If I had money, I would buy a car