Grammar Invasion_Modal verbs (rules)

What are modal verbs?

Modals (also called modal verbs, modal auxiliary verbs, modal auxiliaries) are special verbs which behave irregularly in English. They give additional information about the function of the main verb that follows it. They have a great variety of communicative functions.

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

They follow 3 important rules:

1.  They NEVER change their form. No -s, no -ed, no -ing at the end!!!;

He can go out tonight.
He cans go out tonight.
He can goes out tonight.

2.  They are ALWAYS followed by an infinitive without to (base form);

She should STUDY for the test. 
She should studying for the test. 

3.  You just add NOT for the negative form. No don't, doesn't, didn't, isn't!

You MUST NOT(mustn't) take photographs in class.
You don't must take photographs in class.

Over and out.