USES

Modal verb	Use to...
can	Talk about a skill or possibility in the present, or to ask for permission
could	Talk about a skill or possibility in the past or the future, or to ask for something politely
may	Talk about a possibility in the future or the present, or to ask for something politely
might	Talk about a possibility in the future or the present, or to ask for something politely
will	Talk about something that will be done in the future
shall	Talk about something that will be done in the future
should	Talk about an obligation or a recommendation
ought to	Talk about an obligation or a recommendation
must	To talk about an obligation, a prohibition or a need
would	Speak of a preference or a custom in the past, or to ask something politely

Can

"Can" indicates skill or ability. In these cases it can be translated as "power" in Spanish.

Examples:

I can speak five languages. (I can speak five languages).

We can work late tonight if you need us. (We can work till late tonight if we need to.)

Bill and Tom can't help you. (Bill & Tom not can help you.)

The restaurant can be expensive if you drink a lot of wine. (The restaurant can be expensive if you drink much wine).

It can be dangerous to drive if you are tired. (Driving can be dangerous if you are tired.)

In interrogative sentences, the use of "can" can request permission or ask about the possibilities.

Examples:

Can I have a glass of water? (I take a glass of water?)

Can you help me? (Can you help me?)

Can they work late tonight? (They can work late tonight?)

Could

"Could" indicates possibility or ability in the past.

Examples:

Joe could speak Spanish when I was young. (Joe could speak Spanish when I was young).

I couldn't sleep last night. (I couldn't sleep last night.)

Could you play an instrument when you were a child? (You could touch an instrument when you were a child?)

"Could" can also be used for possibilities in the future.

Examples:

You could pass the test if you studied. (You can pass the exam if you study).

I think it could rain later. (I think it might rain later.)

Such as "can", in interrogative sentences "could" can request permission or ask about the possibilities, but is more formal.

Examples:

Could you pass the salt please? (Could pass me the salt please?)

Could you help me? (Could you help me?)

Could I be wrong? (I could be wrong?)

Note: "Could" is used in conditional sentences. See the lesson on conditional phrases for more information about the use of "could".

May

Such as "could", "may" is used to indicate possibilities in the future.

Examples:

I would bring an umbrella, it may rain later. (It would take an umbrella, it can rain later.)

It may be better to finish this now, rather than wait until tomorrow. (It may be better to end this now, rather than wait until tomorrow.)

It can also be used to give permission or instructions.

Examples:

You may leave if you like. (You can leave if you want to).

You may use your cell phones now. (You can use their phones now.)

In interrogative sentences, the use of "may" is more polite than "can" or "could".

Examples:

May I have a glass of water? (It may take a glass of water?)

May I leave now? (It could exit now?) https://www.microsofttranslator.com/bv.aspx?from=&to=en&a=https%3A%2F%2Fwww.curso-ingles.com%2Faprender%2Fcursos%2Fnivel-basico%2Fverbs%2Fmodal-verbs