is used to talk about an obligation that comes from
outside, that has to be made
Example
I don’t have to buy a house.
You have to read this book
I have to start preparing dinner.
BE ABLE TO
It is used when we want to say that someone is capable
of something, that they can.
Examples
I'd like to be able to run as fast as you do
I will be able to cook delicious dishes after I
finish the cooking course.
MIGHT
Used for suggestions or
possibilities
Example
He might come tonight.
You might as well try to open and
get in the car
Small probability
SHOULD
It is used more when giving advice, making or asking for
suggestions, opinions and actions, or to generate a certain
level of expectation for something future.
Example
You should listen to me.
Should she doesn’t back?
Recommendation/ advice
SHALL
Its meaning is like that of the verb "will", it
expresses something in relation to what may
happen.
Example
We shall dance together soon, my lady.
Shall we go to the cinema?
Future (with I and we)
WILL
is an auxiliary, also known as a modal verb. This
means that we use it to create a form of the verb, in
this case, the future.
Examples
I won't let you pass.
I will call him right now
Future/ prediction
MAY
is used in affirmative or negative sentences, always followed by
an infinitive verb to express probability in the future, and at the
beginning of questions to ask permission with a certain
politeness.
Example
May I talk to you for a minute?
You may feel better after taking the medicine.
They may not accept the offer.
Good probability
MUST
is an auxiliary verb used with an infinitive verb to
express obligation or prohibition.
Example
Must I find the money?
She must take the children with her to Houston
He must not be telling lies
WOULD
We use it when we want to talk about habits or customs of
the past.
Example
Would you turn off the lights when you leave?
I would like to play tennis on Sundays
Request / offer
COULD
This modal verb is the past form of "can". Its
meaning is the same, but the verb tense
expresses something that has already
happened, or it is also used to provide
alternatives.
Example
We could meet up today.
Could you call your mom, please?
Past ability
CAN
You can use it to express some possibility or
request, or to say that you are qualified for
something.
Example
Forgive me, can you tell me what time
is?
I can cook pizza.
He can’t speak of my nervousness
Present ability
OUGHT TO
has the same meaning as should, we can talk about something
that should happen or give good advice.