Modal verbs are used to express modality or the attitude of the speaker towards what is being said. There are several characteristics of modal verbs including that they can form contractions, do not have an infinitive form, do not require third person singular -s, are followed by an infinitive verb without "to", and cannot be conjugated. Common modal verbs that express obligation include must, have to, and need to. Modal verbs are also used to express lack of obligation with don't/doesn't have to, negative obligation with must not/musn't, and uncertainty with might/might not. Questions about obligation use do/does + subject + have to in their formation.

1. ISE I (B1)
MODAL VERBS

2. What is a modal verb?
 Verbs that have the function of expressing
the modality or special value of what you
are saying.
 These values cannot be expressed by the
different verbal tenses.

3. Characteristics of modal verbs:
1. Negative: modal verb + not.
Ex: You must not (mustn’t) tell lies.
2. Interrogative: inversion between verb and
subject.
Ex: Can I go to the concert?
3. They admit contractions.
Ex: can’t, mustn’t, shouldn’t…

4. Characteristics of modal verbs:
4. They don’t have infinitive form.
5. They don’t need to add the –s o the 3rd person
singular.
6. They are followed by a verb in infinitive without
to.
Ex: He could have come to the party
7. They cannot be conjugated.

5. OBLIGATION AND NECESSITY
 We use must, have to and need to +
infinitive.
Examples:
 …you need to hear other people speaking.
 … you have to speak.
 … you must choose things that you’re
interested in.

6. LACK OF OBLIGATION
 We use do/ does not (don’t/doesn’t)
have to + infinitive
 Examples:
 …you don’t have to understand evertyhing to be able
to communicate

7. NEGATIVE OBLIGATION
 We use the modal verb must in the negative
form: must not (musn’t) + infinitive
 Example: …you musn’t get demotivated by
this.
UNCERTAINTY
 We use the modal verb might : might/ might
not + infinitive
 Example: …you might not understand much
at all.

8. QUESTIONS ABOUT
OBLIGATION:
 To ask questions about obligation or
rules, we use: (wh- word) do/ does +
subject + have to + infinitive?
Example: What do I have to do to
really learn a language?