What are modal verbs?

Modals (also called modal verbs, modal auxiliary verb s, modal auxiliaries ) are special verbs which behave irregularly in English. They are different from normal verbs like “work, play visit…” They give additional information about the function of the main verb that follows it. They have a great variety of communicative functions .


Here are some characteristics of modal verbs:

They never change their form. You can’t add “s”, “ed”, “ing”…

They are always followed by an infinitive without “to” (e.i. the bare infinitive.)

They are used to indicate modality allow speakers to express certainty, possibility, willingness, obligation, necessity, ability

List of modal verbs:  can, could, may, might, will, would, shall, should, must .The verbs or expressions dare , ought to, had better , and need not behave like modal auxiliaries to a large extent and may be added to the above list


Use of modal verbs:

Modal verbs are used to express functions such as:

  1. Permission
  2. Ability
  3. Obligation
  4. Prohibition
  5. Lack of necessity
  6. Advice
  7. possibility
  8. probability


Examples of modal verbs

Here is a list of modals with examples:


Strong obligation : You must stop when the traffic lights turn red.

logical conclusion / Certainty

He must be very tired. He’s been working all day long.

must not prohibition : You must not smoke in the hospital.



ABILITY:  I can swim.

PERMISSION : Can I use your phone please?

POSSIBILITY :Smoking can cause cancer.


ABILITY IN THE PAST: When I was younger I could run fast.

POLITE PERMISSION: Excuse me, could I just saysomething?

POSSIBILITY: It could rain tomorrow!


PERMISSION: May I use your phone please?


PROBABILITY: It may rain tomorrow!


POLITE PERMISSION: Might I suggest an idea?


PROBABILITY: I might go on holiday to Australia next year.

need not lack of necessity/vabsence of obligation

I need not buy tomatoes.

There are plenty of tomatoes in the fridge.


50 % OBLIGATION: I should / ought to see a doctor. I have a terrible headache.

ADVICE : You should / ought to revise your lessons

LOGICAL CONCLUSION: He should / ought to be very tired. He’s been working all day long.


Modal verbs are followed by an infinitive without “to”, also called the bare infinitive.


You must stop when the traffic lights turn red.

You should see to the doctor.

There are a lot of tomatoes in the fridge. You need not buy any.


See also

Positive statement to Negative

Rhyme Scheme

Stress and Intonation



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