Expressing Modality in English with the Modal Verb MUST
This is the sixth and last lesson in the modal verbs or modal auxiliaries series.
Today, we are going to talk about the affirmative, negative and interrogative forms of MUST.
REMEMBER:
- There are 9 modal verbs in English: Must, Can, Could, May, Might, Will, Would, Shall and Should.
- Modal verbs are tools that help us to express modality. In fact, modals allow the speaker to express his or her point of view regarding an action, an event or a situation.
- Modal verbs always remain the same no matter the subject and cannot be conjugated. Moreover, they do not have present and past participles. (I
ammustinggo./ Ihavemustedgo.)
Step 1: Characteristics of MUST
- We mostly use the modal verb MUST in the present tense. (E.g. I must go to the post office now.)
- A verb stem always follows MUST. (E.g. You must respect the rules.) The verb stem is also known as the base of a verb. You can find examples of verb stems in the dictionary.
- We do not add ‘TO‘ after MUST. (E.g. We must
tobe careful.) - MUST is able to replace auxiliary verbs such as DO and BE which help us to form questions. (E.g. What must I do to become better in English?)
- MUST can be replaced with the semi-modals HAD TO in the past, HAVE TO in the present and WILL HAVE TO in the future.
Step 2: Examples of MUST in the Affirmative Form (+)
Talking About Obligations
The speaker uses MUST to express a strong sense of duty. We can also talk about legal or moral imperatives.
MUST can be replaced by the semi-modal HAVE TO. Note that with HAVE TO, the obligation is imposed from outside (another person, societal rules, regulations, traditions, customs, etc). (E.g. I have to do my homework. The teacher says so????)
- I must respect the elderly.
- You must do your homework.
- He must send the email by twelve.
Your Turn: Make 3 sentences in which the speaker expresses obligation using MUST.
Expressing Necessity
The speaker can also use MUST to show that it is necessary or required to do something.
We can replace MUST with NEED TO here. With NEED TO, the obligation is less strong (E.g. I need to see the doctor. (I think it is essential that I see the doctor. However, no one is forcing me to see the doctor).
- I must eat more vegetables.
- You must see your friends more. You will feel much better.
- We must do more sports to be healthy.
Your Turn: Make 3 sentences in which you express necessity using MUST.
Making Deductions About the Present
MUST can be used to say that a situation or action is highly probable. We have a high degree of certainty with MUST.
- He must be at home. His car is outside the house.
- They must (really) love each other. They are always together.
- I must have flu. I have been coughing all day.
Your Turn: Make 3 sentences in which you make deductions about the present using MUST.
Making Deductions about the Past
We can also use MUST + HAVE-EN/ED (Present Perfect) to make strong guesses about the past.
- They must have been very happy. You could tell from the way they laughed all the time.
- He must have acted like a jerk for Jane to divorce him. Normally, Jane is such a sweet woman.
- She must have cheated on him. You certainly can’t trust Jane with your husband.
Your Turn: Make 3 sentences in which you make deductions about the past using MUST.
Making Commands
We can equally use the modal verb MUST to give strong orders to someone.
- You must stop singing so loudly. The whole neighbourhood is awake because of you.
- They must come back immediately.
- He must return the borrowed items with immediate effect.
Your Turn: Make 3 sentences in which you express strong commands with MUST.
Making Positive Suggestions or Recommendations
It is possible to use MUST to recommend something to someone.
- The film is absolutely nice. You must see it!
- Jack must try this recipe! It will change his life.
- You must come next summer. I promise, you’ll enjoy yourself very much.
Your Turn: Make 3 sentences in which you make positive suggestions or recommendations to someone using MUST.
Step 3: Examples of MUST in the Negative Form (-)
Expressing Obligations
We can use MUST + NOT to talk about what we cannot do because of duty.
However, note that, here, you cannot replace MUST NOT with DO NOT HAVE TO because they do not have the same meaning. (E.g. I do not have to go the doctor’s. There is no need for you to go the doctor’s. There is a lack of obligation.)
- I must not talk rudely to elders.
- We must not overly criticise our politicians. Sometimes, they do a good job.
- She mustn’t misuse environmental resources.
Your Turn: Make 3 sentences in which the speaker expresses obligations using MUST + NOT.
Expressing Prohibition
The speaker uses MUST + NOT to tell someone that he or she cannot do something.
- You must not watch TV so late at night.
- He mustn’t talk to me like that.
- They must not play video games.
Your Turn: Make 3 sentences in which the speaker expresses prohibition using MUST + NOT.
Making Deductions About the Present
MUST + NOT can be used to say that a situation or action is highly improbable.
- He must not be at home. His car is not outside the house.
- They must not love each other. They are always fighting.
- I must not have flu. I barely have its symptoms.
Your Turn: Make 3 sentences in which you make deductions about what is improbable in the present using MUST + NOT.
Making Deductions about the Past
We can also use MUST + HAVE-EN/ED (Present Perfect) to make strong guesses about what was very unlikely to happen in the past.
- They mustn’t have been happy. You could tell from the way they cried all the time.
- He mustn’t have acted like a jerk for Jane to remain with him. Normally, Jane doesn’t take any nonsense from any man.
- She must not have cheated on him. Jane can’t even harm a fly.
Your Turn: Make 3 sentences in which you make deductions about what was very unlikely to happen in the past using MUST + NOT.
Making Negative Suggestions or Recommendations
It is possible to use MUST + NOT to say that someone had better not do something.
- The food in this restaurant is horrible. You mustn’t eat it.
- You must not go out with Jack. He is a good-for-nothing boy and he will break your heart.
- He mustn’t work so hard. It’s not worth ruining his health for that.
Your Turn: Make 3 sentences in which you make negative suggestions or recommendations using MUST + NOT.
Step 4: Examples of MUST in the Interrogative Form(?)
Asking Questions About Obligations
We can use MUST to inquire if we have to do something or not out of duty. We can replace this with DO WE HAVE TO…?
- Must I go to bed so early? (Do I have to go home so early?)
- Sir, must we hand in our homework now?
- Must he really stop drinking?
Your Turn: Make 3 sentences in which you ask questions about obligations using MUST.
Asking Questions About Necessity
Sometimes, we can use MUST to ask someone if it is necessary or required to do something.
- Must we take vitamins all the time?
- Madam, must we wait for you?
- Must I do this?
Your Turn: Make 3 sentences in which the subject asks questions about necessity using MUST.
Asking for Information
We can equally use the modal verb MUST to get information about what we are obliged to do or what is necessary to do.
- What must we do exactly? (E.g. Students asking a teacher)
- How long must I take this medicine.
- When must we go?
Your Turn: Make 3 sentences in which the subject asks for information using MUST.
Making Criticisms
We can use MUST to express disapproval of something or someone.
- Must you talk so loudly?
- Must this be so tough?
- Why must you rub my failure in my face?
Your Turn: Make 3 sentences in which the subject criticises someone or something using MUST.
Further Exploration:
Download worksheets:
- English Grammar (Modal Verbs or Modal Auxiliaries): Lesson 6-The Modal Verb MUST (with examples!), Learn English With Africa, February 2021
- English Grammar (Modal Verbs or Modal Auxiliaries): Lesson 6-The Modal Verb MUST (PowerPoint)
Read:
Watch: The Modal Verb Must in English