The modal verbs in English are can, could, may, might, shall, should, will, would, and must. Each modal verb has several different meanings, e.g. can can express both ability and permission:

The youngest player can start the game.

Modal verbs (e.g. should) are auxiliary verbs that usually express things like ability, possibility, or permission. They are followed by a main verb in bare infinitive form (e.g. know):

Everybody should know the rules of this game.

Modal verbs are different from regular verbs: they don’t get the third person singular –s-ending and they don’t have –ing or –ed forms.

Use modal verbs can and could when requesting something. Note that could is more formal and polite than can. Could is is the past tense of can. It expresses ability in the past:

My father could beat everybody in swimming competitions when he was young.

May expresses possibility and can also be used to ask for permission. When asking for permission, may is more polite than can, but can is more common:

They may lose this game.

May I speak to the referee, please?

Might is almost the same as may: it expresses possibility and permission:

He might get a penalty for delaying the game.

The modal verb must is used to express a strong obligation and a logical conclusion:

You must respect your teammates.

Thomas went to the snack bar so he must be hungry.

Remember that the word order of an interrogative sentence is 1. auxiliary verb 2. subject 3. main verb 4. object:

Can we order Chinese takeaway?

Shall is used in questions to make suggestions or offers:

Shall we go skateboarding?

The modal verb should is used in recommendations, suggestions, and to ask for or give advice:

You should buy a new hockey stick, that one is so old.

Will is used to express future plans and it can be used to make promises. Will can also be used to make predictions about the future. Modal verbs are often complemented by adverbs such as surely:

This court will be renovated next year.

Tobias will surely catch the ball.

Would is the past tense of will. It can be used to talk about a past habit:

When we were kids, we would play rugby every day.

Use the construction would you like when enquiring something from someone. It is more polite than to use the verb want:

What would you like for dessert?