Modal verbs are auxiliary verbs that express ability, permission, possibility or necessity. They are used to talk about the future or conditions and include verbs like can, could, may, might, will, shall, should, ought to, must, have to and would. Modal verbs are not conjugated and are always followed by another verb in its base form. Some common uses of modal verbs are to indicate ability or possibility with can and could, request permission with can and could, and talk about past ability or possibility with could.

1. MODAL VERBS

2. What are they?
Modal verbs are auxiliary verbs that can not function as a main verb, unlike the auxiliary verbs
"be", "do" and "have" that can function as a main verb.
Modal verbs express modality, ability, possibility, need or other condition. We use them for the
future and the conditional.
As complementary verbs that are, modal verbs do not work without another verb. This other
verb always goes after the modal verb and is in the base form (the infinitive without "to").
Modal verbs are not conjugated and do not have time

3. Modal verbs are
Can
 could
 may
 might
 will
shall
 should
 ought to
 must/have to
 would

4. USES
1. CAN: indicates ability or possibility.
Examples:
I can speak five languages
 We can work late tonight if you need us
 Bill and Tom can’t help you.
In interrogative phrases, the use of "can" can request permission or ask about possibilities.
Examples:
Can I have a glass of water?
Can you help me?
 Can they work late tonight?

5. 2. Could: "Could" indicates possibility or ability in the past
Examples:
 Joe could speak Spanish when he was young.
 I couldn’t sleep last night.
 Could you play an instrument when you were a child
You can also use "could" for future possibilities.
Examples:
 You could pass the test if you studied.
 I think it could rain later.

6. As "can", in interrogative phrases "could" can request permission or ask about the possibilities,
but it is more formal
Examples:
Could you pass the salt please?
Could you help me?
Could I be wrong?