Must

We use modal verbs to show if we believe something is certain, probable or possible (or not). We also use modals to ask permission, make requests and offers etc.

Modal verbs fall into the category of auxiliary verbs (also known as helping verbs). It means that they are used together with a main verb to give grammatical information and additional meaning to a sentence.

We use the modal verb must and the base form of the verb to form sentences. Questions are formed by inverting the subject and must. Negatives are formed with not. Contracted forms are used (mustn't).

We can use the modal verb must:

to express obligation, duty, or prohibition (this also refers to laws and regulations)

You must wear a seatbelt at all times
You mustn't use your smartphone while driving

to emphasize the necessity of something.

People must drink a lot of water during the day

to express our certainty in something being true.

Look! There are puddles everywhere. It must have rained
You are still working? You must be tired!

to give a strong recommendation.

You must listen to this song, it's so catchy!

May

You can use the modal verb may:

to give permission or prohibit something

If you have finished the test, you may leave the room
You may not park here

to ask for permission (more polite than can)

May I use your bathroom, please?

to express wishes

May you both live happily!

in academic (or sciencific) languange to refer to things that typically happen in certain situations.

Drivers may feel tired after driving for 3 hours straight

Note that we usually use the modal verbs may and might without a significant difference in meaning when expressing possibility. However, might often implies a smaller change of something happening.

I might go to the movies tonight. I'm not sure.

Guided Practice

Use must to express obligation, duty, or prohibition.

You .................... gossip about your coworkers.

Use must to emphasize the necessity of something.

Kate .................... go to the doctor. She looks ill.

Use must to express certainty in something being true.

John didn't call me last night. He .................... have been busy.

Use may to ask for permission.

.................... I open the curtains? It's quite dark here.

Use may or might to expressing possibility.

We .................... go to China for your honeymoon. We are still thinking about it.

–Do you know why I've been feeling so sick lately?

–I'm not a doctor. You must set an appointment with one.

–No, I'm fine. I must be tired from working 12 hours a day.

–It may be, but you must go to the doctor anyway!

–I'll try to sleep more.

–You know what it might get worse, right? Should I come along?

–That would be great actually!

Independent Practice

Fill in the gaps with must or may.

The lights are out. They .................... have gone out.
.................... I borrow your pen, please?
You .................... go once you fill out the papers.
We .................... go now. Otherwise we'll miss our flight.

Match the sentences.


a. You may not cross the street here.	1. I might go to a dinner party next week.
b. Will you be at home at 8?	2. The traffic is crazy.
c. May I borrow your red dress?	3. I might stop by.

React to the situations. Form sentences using must or might.

Your friend is trying to park his car. Tell him that there is a sign "No Parking" nearby.
Your sister is baking a cake. Tell her to follow the recipe.
You want to go to the movies with your friend buy you're not sure if it is still on.

Must - May - Might

Must

May

Guided Practice

Short Story using Modal Verbs Must - May - Might

Independent Practice

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