Modals are different from normal verbs:
1: They don’t use an ‘s’ for the third person singular.
2: They make questions by inversion (‘she can go’ becomes ‘can she go?’).
3: They are followed directly by the infinitive of another verb (without ‘to’).
!Note The modal auxiliary verbs are always followed by the base form.
Must
Must” is most commonly used to express certainty. It can also be used to express necessity or strong recommendation, although native speakers prefer the more flexible form “have to.” “Must not” can be used to prohibit actions, but this sounds very severe; speakers prefer to use softer modal verbs such as “should not” or “ought not” to dissuade rather than prohibit.
Examples:
- This must be the right address! certainty
- Students must pass an entrance examination to study at this school. necessity
- You must take some medicine for that cough. strong recommendation
- Jenny, you must not play in the street! prohibition
REMEMBER: “Must not” vs. “Do not have to”
“Must not” suggests that you are prohibited from doing something.
“Do not have to” suggests that someone is not required to do something.
Examples:
- You must not eat that. It is forbidden, it is not allowed.
- You don’t have to eat that. You can if you want to, but it is not necessary.
Have To
“Have to” is used to express certainty, necessity, and obligation.
Examples:
- This answer has to be correct. certainty
- The soup has to be stirred continuously to prevent burning. necessity
- They have to leave early. obligation
May
“May” is most commonly used to express possibility. It can also be used to give or request permission, although this usage is becoming less common.
Examples:
- Cheryl may be at home, or perhaps at work. possibility
- Johnny, you may leave the table when you have finished your dinner. give permission
- May I use your bathroom? request permission
Might
“Might” is most commonly used to express possibility. It is also often used in conditional sentences. English speakers can also use “might” to make suggestions or requests, although this is less common in American English.
Examples:
- Your purse might be in the living room. possibility
- If I didn’t have to work, I might go with you. conditional
- You might visit the botanical gardens during your visit. suggestion
- Might I borrow your pen? request
REMEMBER: “Might not” vs. “Could not”
“Might not” suggests you do not know if something happens. “Could not” suggests that it is impossible for something to happen.
Examples:
- Jack might not have the key. Maybe he does not have the key.
- Jack could not have the key. It is impossible that he has the key.
