Modal verbs are used to change or complete the meaning of the main verb. They express concepts like ability, possibility, deduction, obligation, prohibition, and advice. Modal verbs don't use third person singular 's' and are followed by the basic form of another verb. They don't change spelling or have infinitives or participles. Negation uses 'not' rather than a form change. Examples are given for ability (can, could, be able to), possibility (may, might, could), deduction (must, can't), obligation (have to, must), prohibition (must not), and advice (should, ought to).

1. MODAL VERBS
Teacher Emerson Macedo

2. Modal verbs
• They are a special kind of verb that change or complete the meaning of the
main verb.
• They can express ability, possibility, deduction, obligation, prohibition, advice
and etc.
• They don’t use an “s” in the third person singular.
• They are directly followed by another verb in the basic form (infinitive
without “to”).
• They do not change their spelling and they have no infinitive or participle.
• You use "not" to make modal verbs negative, even in Simple Present and
Simple Past.

3. Ability
• can / could / be able to
It can help the athletes in their trainning program. (present)
Ordinary tape could help injuries heal. (past)
He’ll be able to play the game next weekend.

4. Possibility
• may / might / could
It may work on humans
Some people might choose modern medicine.
He could choose a natural anternative.

5. Deduction
• must / can’t
Having a sport injury must be frustrating.
 Some people say these therapies can’t be as effective as modern
medicine.

6. Obligation
• have to / must
He has to practice more.
 First, they must train harder.

7. Prohibition
• must not
You must not lose the game today.

8. Advice
• should / ought to
You should practice for the game. It’s going to be difficult.
You ought to run faster.