Modal Verbs

1. Must

1.1. Obligation

1.2. Certainty

1.3. Logical assumptions

1.4. A strong recommendation

2. Should

2.1. Advice

2.2. Prediction

2.3. Less strong obligation

3. Shall

3.1. Suggestion

3.2. Offers / Volunteering to do something

3.3. Instructions

3.4. Promises

3.5. Formal written regulations and rules

4. Have to

4.1. Obligation, necessity

4.2. Deduction, logical assumption

4.3. Advice or recommendation

5. Can

5.1. General ability

5.2. Permission

5.3. Request

5.4. Possibility

5.5. Probability (0%)

5.6. Offer

6. May

6.1. Polite request

6.2. Polite permission

6.3. Prohibition

6.4. Wish

7. Would

7.1. Polite invitation

7.2. Describe a prediction

7.3. To not sound impolite when disagreeing with someone

7.4. To describe past habits

8. Ought to

8.1. Obligation

8.2. Assumption, probability

8.3. Advice

8.4. Regret and reproach