What are modal verbs?
Modals (also called modal verbs, modal auxiliary verbs, modal auxiliaries) are special verbs which behave irregularly in English. They are different from normal verbs like “work, play, visit…” They are used to indicate modality. They give additional information about the function of the main verb that follows it. They have a great variety of communicative functions.
Use of modal verbs:
Modal verbs are used to express functions such as:
Lack of necessity
Modal verbs are followed by an infinitive without “to”
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.
You ought to go to the doctor