Must & Have to

In English, there are modal verbs that we can use to describe rules and obligations. Describing rules and obligations has always been so tricky, especially for students. 

In this lesson, you are going to learn two modal verbs ( must and have to) that help us in expressing rules and obligation. You will know how and when to use them. 

Must and have to are almost similar, both have the same usage, but there is a slight difference between them which I will cover in this lesson.

But first of all, you need to understand two terms.

Personal obligations 

Personal obligations are those things or actions that the speaker finds necessary to do. They are not imposed by general authorities but by specific authorities to specific people. 

Objective obligations:

Objective obligations are impersonal obligations. The subject is forced by some external power to act on them. They are imposed by others such as government, school rules etc. 

Must 

Must is a present tense modal verb that is used to express three things. 

1. Obligations 
2. Necessity 
3. Responsibility 

We use must to express personal obligations, necessities and responsibilities. We use it when obligations are not imposed by others (law). By using ‘must’, we represent directly that something is necessary to be obliged. There’s no choice for the speaker to surpass those obligations. You can think of obligation as more of a person or someone’s opinion. 

‘must’ is only used in present time or in the near future to describe a general obligation. 

Structure:

The structure of ‘must’ is quite easy as it follows the same pattern for every subject. 

Examples of obligations using ‘m

• You must complete your homework today. 
• He must wash the car. 
• I must write a letter to the principal. 
• They must bring the books tomorrow. 

Examples of necessity using ‘must.’

• He must control his anger, else he will regret someday. 
• The uniform must be pressed.
• You must perform wudhu before prayer. 
• You are sick; you must see a doctor. 
• I must work hard to pass the test. 

Examples of responsibility using ‘must.’

• I must pray on time. 
• You must wash the dishes. 
• He must take out the trash every day. 
• They must clean the garden.

Prohibition-mustn’t  

To prohibit someone from something we use 'must not' often contracted as 'mustn't.'  'Mustn't' express strong obligations.  But here prohibition can be the speaker's personal opinion or law or anybody else in higher authority than you. You can use 'mustn't' to talk about the present or near future. 

Example: 

(Objective)

• You mustn’t park your bike here. 
• You mustn’t sleep late at night.
• Students mustn’t rush towards cafeteria; they will hurt themselves. 
• He mustn’t use his mobile during the lecture. 

(subjective)

• I must not annoy him. 
• I must not eat junk food anymore. 
• I mustn’t cross the road while it’s red light yet. 

Questions 

'Must' can be used in questions, but it's very uncommon to use must in questions. 

Structure:

Must + subject+ verb+?

Examples:

• Must you keep on irritating me? I am losing my patience.
• Must I go to school? I am exhausted today. 

Have to

'Have to' is not a modal verb but, for the ease, it is considered as a modal verb in some specific situations in English grammar. Likewise 'must' it is also used to express three things 

1. Obligations 
2. Necessity 
3. Responsibility 

However, it is used to express general obligations. Such obligations are also called external obligations that are not said or in control of the speaker but are mandatory to follow as law or set of rules.

External obligations cannot be changed. 'have to' is used in the present tense, past tense and in future time. It is more flexible than 'must' in terms of its usage in more than one tense. 

The structure of 'have to' is the same for all the subjects. 

Example: Obligations using ‘have to.’ 

Here the obligations are imposed by some other person but not the speaker. 

• I have to write a report. (a teacher gives a command)
• We have to wear a tie within the premises of the school. ( a rule imposed by all schools)
• We have to wear a seat belt while driving. ( a traffic rule)
• In Pakistan, students have to wear black shoes in schools. ( Pakistani school rule)
• She has to pay school fee every year. 

Example: necessities using ‘have to.’

• You have to leave the office now. 
• He has to wear a black shirt at the party. It’s a dress code. 
• You have to work hard if you want to score higher than Paul in the final test. 

Example: responsibility using ‘have to.’

• I have to buy fruits for my mother. 
• I have to pick my sister from school.
• You have to collect all the reports. 
• They have to decorate the room for a birthday party. 
• I will have to make breakfast tomorrow at 7.00 am. ( future time)

No obligations- don’t have to 

Here don’t have gives the sense that there is no obligation. You are not required to oblige. ‘don’t have to’ isn’t similar to ‘mustn’t’ which is used to express strong prohibitions. 

Example: 

• I don’t have to wear a mask in the office.
• You don’t have to complete the tasks today. 
• He doesn’t have to pay the school fee. It’s free.
• They don’t have to attempt all of the questions.
• She doesn’t have to wear a helmet while riding a bicycle. 
• We didn’t have to use our pens in the test. The teacher provided us. ( past tense)

Questions 

You can make questions using 'have to', they are more common as compared to questions with 'must'.

Example: 

• Do you have to leave right now?
• Did you have to complete this lab manual?

Note: In informal English, have got to is sometimes used instead of 'have to.'

• I have got to clean my room before studying. 

Conclusion:

In this lesson we have learned many essential things which are:

1. Must is used for specific/ internal obligations or what speakers thinks is necessary to do. 
2. Mustn’t is used to express the idea of prohibition. 
3. Have to is used for a general obligation or external obligations.
4. Don’t have to is used to show that there are no obligations. 

Exercise:

Choose the correct answer:

1. Bicyclists _____ use the left lane.
2. Have to 
3. Must 
4. Mustn’t 
5. Has to 
6. The salesmen _____  wear a cap. 
7. Have to 
8. Must 
9. Mustn’t 
10. Has to 
11. He ____ smoke in the lobby. It’s prohibited. 
12. Don’t have to 
13. Must 
14. Mustn’t 
15. Had not 
16. All students ____ well dressed for the independence day celebrations. 
17. Have to 
18. Must 
19. Must be 
20. Mustn’t be 
21. I _____ complete my assignments on time.
22. Must 
23. Have to 
24. Mustn’t 
25. All of the above 

Answer key:

1. B 
2. A
3. C 
4. B 
5. A