Have to | Can | Should | Must

1. Have to 2. Can 3. Must 4. Should

MODALS

HAVE TO and CAN

I have to wake up early to my class.

It´s necessary

I don't have to wear a uniform.

It's not necessary.

You can use your phone for our class.

We use have to / don't have to / doesn't have to to talk about rules and things we need or don't need to do.

It's possible

You can't copy and paste your sentences.

We use can when something is allowed and can't when it is prohibited or not possible.

It's not possible

HAVE TO Structure Affirmative

HAVE TO Structure Negative

HAVE TO Structure Interrogative

When do you have to wear your uniform?

CAN Structure Affirmative

CAN Structure Negative

CAN Structure Interrogative

When can you call me?

I must stop eating so much

MUST or MUSTN'T

Expresses obligation from a subjective point of view, such as a natural, social or administrative law (rules, procedures, manuals).

He must learn to drive. it will be very useful

Subject + must/mustn't + verb + complement

MUST Structure Affirmative

MUST Structure Negative

MUST Structure Interrogative

SHOULD or SHOULDN'T

Good idea

You should learn a new language.

We use should to give and ask for advice.

You shouln't drink tap water.

Bad idea

SHOULD Structure Affirmative

SHOULD Structure Negative

SHOULD Structure Interrogative

When should I call you?

Have to

Must

Should

Have to, can, should