Ought to is used to advise or make recommendations, and also expresses assumption or expectation. Must is used to express certainty or necessity. Had better is commonly used to make recommendations, but can also express desperate hope or serve as a warning. Examples provided illustrate the uses of ought to for recommendations and probability, must for certainty, necessity, strong recommendation and prohibition, and had better for recommendations, desperate hope, and warnings.

1. MODAL VERBS
1) USE OF OUGHT TO
2) USE OF MUST
3) USE OF HAD BETTER

2. USE OF OUGHT TO
• It is used to advise or make recommendations.
• It is also expresses assumption or expectation as well as strong probability,
often with the idea that something is deserved.
• Ought not (without “to”) is used to advise against doing something.
Examples:
• You ought to stop smoking. Recommendation
• This stock ought to increase in value. Probability

3. USE OF MUST
• It is most commonly used to express certainty.
• It can also be used to express necessity, strong recommendation and
prohibition.
• It indicates that the speaker is certain about something.

4. Continue…..
Examples:
• This must be the right address! CERTAINTY
• Students must pass an entrance test to study at this University. NECESSITY
• You must take some medicine for that cough. STRONG
• Ali, you must not play in the street! PROHIBITION

5. USE OF HAD BETTER
• It is the most commonly used to make recommendations.
• It can also be used to express desperate hope as well as warn people.
Examples:
• You had better take your umbrella with you today. RECOMMENDATION
• That bus had better get here soon! DESPERATE HOPE
• You had better watch the way you talk to me in the future! WARNING