Modal Verb - Must
Modal verbs are auxiliary verbs used to express ideas such as (necessity, ability, possibility, advice, obligation, probability, requests, permission, etc.), in English they are combined with verbs in their infinitive forms. Modal verbs have their own question and negation forms, they do not depend on the auxiliary verb -do for this purpose. Modal verbs in English include (-can, -could, -will, -would, -should, -must, -may, and -might), the modal verbs -ought to and -shall are antiquated and are not regularly used in modern English.
Note: The modal verb -must is also expressed with the phrases have to + infinitive, need to + infinitive, and got to + infinitive.
The modal verb -must is used to:
1) To express the necessity of completing an action (obligation).
2) To make strong assumptions based on logic.
3) To make strong recommendations & give commands.
4) To express strong prohibitions.
Formation - Affirmative Statements
The modal verb -must is only used in the present tense, it is used most often in affirmative statements to express a subject's obligation to complete an action. Modal verbs are never conjugated depending on the subject, they remain the same for all subjects which makes them simple to use, modal verbs are always combined with a main verb in the infinitive form.
Structure used to form affirmative statements in the simple present with the modal verb -must.
Subject + must + main verb in the infinitive form
Structure used to form affirmative questions in the simple present with the modal verb -can.
Must + Subject + main verb in the infinitive form?
Examples
Ex: I must leave before the meeting begins.
Ex: Must she make a phone call now?
Ex: We must be careful when picking a supplier.
Ex: John and Danny must go to work this weekend.
Formation - Negative Statements
The modal verb -must is only used in the present tense, it is used most often in negative statements to express a subjects inability to complete an action. Modal verbs are never conjugated depending on the subject, they remain the same for all subjects which makes them simple to use, modal verbs are always combined with a main verb in the infinitive form. Negative statements and questions in the present tense with the verb -be and modal verbs are not formed with the verb -do, they have their own question and statement forms. Negative questions and statements with contractions of -must are almost never used. Negative questions are meant to express surprise, confirm information, or encourage agreement.
Structure used to form negative statements in the simple present with the modal verb -can.
Subject + must not + main verb in the infinitive form
Structure used to form negative questions in the simple present with the modal verb -can.
Must + Subject + not + main verb in the infinitive form?
.
Examples
Ex: We must not take what we have for granted.
Ex: You must not start until we tell you to.
Ex: Must Charles not do any physical strenuous activity?
Ex: I must not spend more than 200 dollars.
Must - Uses
To express the necessity of completing an action (obligation)
Note: Affirmative statements are used in this context, negative statements are used to express prohibitions, however negative questions can be used in this context.
Examples
Ex: I must submit my tax returns by next week.
Ex: Mark must take a makeup test tomorrow.
Ex: Must Katherine decide by tomorrow?
Ex: Must you take you medication now?
Ex: Companies must put their customers first.
Ex: Yesterday, our boss said we must work faster.
Ex: Must Mike not stop smoking after what his Doctor told him?
Ex: You must work hard if you want to succeed.
To make strong assumptions based on logic
Note: Questions should not be used in this context.
Examples
Ex: It must be difficult to open a new business.
Ex: Driving to Florida must take at least 20 hours from here.
Ex: His injury must hurt a lot.
Ex: James must not like his new position at the company.
Ex: She must know how to fill out these forms.
Ex: Kate must not think it's a good idea.
Ex: It must get very humid here in the summer.
Ex: He must believe it's better to wait.
To make strong recommendations & give commands
Note: The subjects -you and -we are used in this context. Questions are not used in this context, however negative statements are for making recommendations.
Examples - Strong recommendations
Ex: You must try the milkshakes here, they're delicious.
Ex: We must meet up on the weekend, I have a lot to tell you.
Ex: You must not spend too much time working, you could stress yourself out.
Ex: We must not keep them waiting, they might think we're being rude.
Examples - Give commands
Ex: You must leave now.
Ex: You must shut the engine off.
Ex: You must tell me what happened.
Ex: You must sign here.
To express strong prohibitions
Note: Negative statements are used in this context, questions and affirmative statements are not.
Examples
Ex: Visitors must not step on the grass.
Ex: You must not speak unless spoken to.
Ex: Employees must not accept tips.
Ex: Mark must not be told about what we plan to do.
Ex: They must not allow him in.
Ex: Kelly must not eat sugary foods.
Ex: I must not take any medication until after the surgery.
Ex: Students must not leave their lockers unlocked.
Must - Using -must at the end of statement to confirm information
The modal verb -must may be added to the end of a statement made with the modal verb -must to confirm information, note that affirmative statements use negative questions with the modal verb -must and negative statements use affirmative questions with the modal verb -must.
Examples
Ex: Charles must be exhausted, must he not?
Ex: Sarah must not go to work this weekend, must she?
Ex: You must renew your membership today, must you not?
Ex: It must be about to rain, must it not?
Must - Alternative phrases
The phrases have to, need to, and got to can be used instead of the modal verb must. Unlike the modal verb must the phrases have to and need to can be used in the past and future tenses making them very useful, like -must, the phrase got to may only be used in the present tense. The phrases have to and need to must agree with the subject in the present tense, all three phrases have to, need to, and got to can be used the same way as -must except for expressing prohibitions which is exclusively done with -must. The phrases have to, need to, and got to are combined with the infinitive form of a main verb.
Past
Examples of the phrases have to and need to implying obligation in the past
Note: Negative statements in simple past imply that an action was optional or unnecessary not that it was prohibited.
Examples with had to
Ex: I had to do a lot of homework yesterday
Ex: We had to pick up my brother from the airport last night.
Ex: Drivers had to take a detour while work was being done on the highway.
Ex: Did you have to work yesterday?
Ex: Didn't Paul have to give you an update?
Ex: The school had to shut down because of the snow storm.
Negative examples with had to
Ex: I didn't have to go school today - Implies the action was unnecessary
Ex: I didn't have to wake up early today - Implies the action was optional
Ex: Marissa didn't have to go shopping this week - Implies the action was optional or unnecessary
Ex: My neighbor didn't have to help me with taking care of my pet, but he did. - Implies the action was optional
Examples with needed to
Ex: I needed to do a lot of homework yesterday
Ex: We needed to pick up my brother from the airport last night.
Ex: Drivers needed to take a detour while work was being done on the highway.
Ex: Did you needed to work yesterday?
Ex: Didn't Paul need to give you an update?
Ex: The school needed to shut down because of the snow storm.
Negative examples with needed to
Ex: I didn't need to go school today - Implies the action was unnecessary
Ex: I didn't need to wake up early today - Implies the action was optional
Ex: Marissa didn't need to go shopping this week - Implies the action was optional or unnecessary
Ex: My neighbor didn't need to help me with taking care of my pet, but he did. - Implies the action was optional
Examples of the phrases had to to make strong assumptions based on logic in the past
Note: This context is expressed with affirmative statements, also, we must use the phrase had to not needed to.
Examples
Ex: That had to hurt.
Ex: The ending had to be very disappointing to long time fans.
Ex: He had to wonder where everyone went.
Ex: The flood had to have caused massive damage.
Ex: The project had to take at least 3 months to complete.
Ex: Jennifer had to feel so happy when she got married.
Present
Examples of the phrases have to, need to, and got to implying obligation in the present
Note: Negative statements in simple present imply that an action is optional or unnecessary not that it is prohibited.
Examples with have to
Note: Native speakers often use the contraction -hafta instead of saying have to, this is informal and grammatically incorrect but used in spoken English.
Ex: I have to make a deposit.
Ex: She has to decide which company she wants to work for.
Ex: International importers don't have to pay tariffs anymore.
Ex: Do you have to take a test today?
Ex: Doesn't James have to go to court this week?
Ex: We have to start preparing for tonight's event.
Ex: Does the company have to give people refunds?
Ex: They don't have to study today.
Examples with need to
Ex: I need to make a deposit.
Ex: She needs to decide which company she wants to work for.
Ex: International importers don't need to pay tariffs anymore.
Ex: Do you need to take a test today?
Ex: Doesn't James need to go to court this week?
Ex: We need to start preparing for tonight's event.
Ex: Does the company need to give people refunds?
Ex: They don't need to study today.
:
Examples with got to
Note: Native speakers often use the contraction -gotta instead of saying got to, this is informal and grammatically incorrect but used in spoken English. With third person singular subjects (she, he, it, singular noun), we must use the phrase has got to with affirmative statements.
Ex: I got to make a deposit.
Ex: She has got to decide which company she wants to work for.
Ex: International importers don't got to pay tariffs anymore.
Ex: Do you got to take a test today?
Ex: Doesn't James got to go to court this week?
Ex: We got to start preparing for tonight's event.
Ex: Does the company got to give people refunds?
Ex: They don't got to study today.
Future
Examples of the phrases have to & need to implying obligation in the future
Note: Negative statements in simple future imply that an action is optional or unnecessary not that it is prohibited. This context may be expresses using the modal verb will or the structure "be going to".
Examples with have to
Ex: I will have to cook tomorrow.
Ex: We are going to have to review the proposal.
Ex: Mark isn't going to have to spend money on repairs, his landlord will.
Ex: Will they have to show ID to get in?
Ex: Won't Paul have to present his idea at the meeting?
Ex: I won't have to waste anymore time with processing payments manually.
Ex: Is my client going to have to appear in court?
Ex: Sandra will have to take the bus while her car is in the shop.
Examples with need to
Ex: I will need to cook tomorrow.
Ex: We are going to need to review the proposal.
Ex: Mark isn't going to need to spend money on repairs, his landlord will.
Ex: Will they need to show ID to get in?
Ex: Won't Paul need to present his idea at the meeting?
Ex: I won't need to waste anymore time with processing payments manually.
Ex: Is my client going to need to appear in court?
Ex: Sandra will need to take the bus while her car is in the shop.
Note: Negative contractions in statements and questions are not typical with the modal verb must in modern English, they are antiquated.