Modal verbs

We use CAN to ask or give permissions, to talk about our abilities or general truths.

Affirmative form - We use can before the base form of the verb to say that

• I can play the guitar.
• She can sing.
• They can take the train to London.

Negative form - We use CANNOT/CAN'T before the base form of the verb (CANNOT is used in formal context):

• I cannot/can't play the guitar.
• He cannot/can't sing.
• They cannot/can't take the train to London.

Interrogative form - We use CAN before the subject, which is then followed by the base form of the verb:

• Can I go to the party?
• Can she sing?
• Can they take the train to London?

We use MUST to express strong obligation and necessity.

Affirmative form - We use MUST before the base form of the verb:

• I must go.
• She must study.
• They must behave.

Negative form - We use MUST NOT/MUSTN'T before the base form of the verb:

• You must not/mustn't leave any rubbish left.
• He must not/mustn't say bad words.
• They must not/mustn't behave like that.

Interrogative form - We use MUST before the subject, which is then followed by the base form of the verb:

• Must I go?
• Must he do that?
• Must they be quiet?

We use HAVE/HAS TO to refer to obligations which come from outside the speaker.

Affirmative form - We use HAVE TO before the base form of the verb:

• I have to pay an extra rent.
• She has to do the exam.
• We have to take our shoes off.

Negative form - We form the negative form DO/DOES NOT/DON'T/DOESN'T:

• I do not/don't have to pay an extra rent.
• She does not/doesn't have to do the exam.
• We do not/don't have to take our shoes off.

Interrogative form - We use DO/DOES in questions too:

• Do I have to pay an extra rent?
• Does she have to do the exam?
• Do we have to take our shoes off?

We use SHOULD to talk about what is the best thing to do in a situation.

Affirmative form - We use SHOULD before the base form of the verb:

• I should go.
• She should listen more.
• They should be less competitive.

Negative form - We use SHOULD NOT/SHOULDN'T before the base form of the verb:

• I shouldn't stay.
• She shouldn't listen to what they say.
• They shouldn't be so competitive.

Interrogative form - We use SHOULD before the subject, which is then followed by the base form of the verb:

• Should I stay?
• Should she listen to what they say?
• Should they be less competitive?