1. Modal Verbs
Should vs. Have to

2. Modal verbs of obligation:
Have to (and must):
We can use have to, must express obligation. This means there is no other choice, or bad things will happen if this is not done.
have to + infinitive
must + infinitive

3. HAVE TO: (strong obligation)
Have to is often used when the speaker feels a requirement or we use have to when the speaker feels that something is necessary.
I have to study today. (there is a big test tomorrow)
I have to go to the doctor. (I am in a lot of pain)
You must exercise. (doctor says)
You must be quiet. (teacher says)

4. Must not :
Must not is used to express negative obligation (an obligation not to do something ) Or We use must not to say that something is a bad idea .
You must not drop those glasses . They’ll break .
You must not wear your best clothes . You’ll get them dirty .

5. Negative And Question Form:
Negative form : “don’t/ doesn’t have to” means no obligation , It’s OK if you don’t. Question form : Do/ Does +subject + have to + verb + ….
You don't have to eat anything you don't like.
I don't have to work on Sundays.
Do I have to do it for Monday ?
Does she have to work for Sunday ?

6. Must:
+ : subject + must + verb +….
- : subject +mustn’t+ verb+ ….
? : not used
Must use in present tense but must has no past tense form , so change to “had to” (past form of “have to” ).

7. Have to :
*Present :
Have / Has to - don’t/doesn’t have to - do / does … have to
*Past :
Had to – didn’t have to – did … have to –
*Future :
For future with “will” only use “will have to”
not Will must

8. Advice And Recommendation :
"Should" is most commonly used to make recommendations or give advice. It can also be used to express obligation as well as expectation.
Examples:
When you go to Seoul, you should visit Gyeongbok Palace. recommendation
You should focus more on your family and less on work. advice
I really should be in the office by 8:00 AM. obligation
By now, they should already be in New York. expectation

9. Advice And Recommendation :
Should + p.p. verb :
We use these forms when someone didn't do the right thing.
Example :
We didn’t play very well . We should have played better .
I got lost .~ sorry . I should have drawn you a map .
It was a lovely old building . They shouldn’t have knocked it down .

10. Fill in the blanks using have/has to, must not, should, or should not.
She lives far from school, so she ____________ leave early every morning.
You __________ turn on the light, it’s sunny.
I can’t remember his address, so I _____ look it up before I go to see him.
The shops here don’t deliver, we _______ carry everything home ourselves.
You ____________ wear that shirt, it doesn’t look very good on you.
You ___________ drink that, it’s poisonous.
Tell her that she _________ be here by six o’clock, or I will leave without her.
You ________ visit Paris someday, it’s beautiful!
You ________ walk alone here at night, it’s too dangerous!
You _______ clean the windows, the maid is coming tomorrow.

11. Fill in the blanks using have/has to, must not, should, or should not.
1. She lives far from school, so she ____________ leave early every morning.
has to
2. You __________ turn on the light, it’s sunny.
don’t have to
3. I can’t remember his address, so I _____ look it up before I go to see him.
have to
4. The shops here don’t deliver, we _______ carry everything home ourselves.
5. You ____________ wear that shirt, it doesn’t look very good on you.
shouldn’t

12. Fill in the blanks using have/has to, must not, should, or should not.
6. You ___________ drink that, it’s poisonous.
must not
7. Tell her that she _________ be here by six o’clock, or I will leave without her.
has to
8. You ________ visit Paris someday, it’s beautiful!
should
You ________ walk alone here at night, it’s too dangerous!
You _______ clean the windows, the maid is coming tomorrow.
don’t have to

13. Practice with your partner
Tell your partner about something you have to do soon for school.
Tell your partner about a restaurant you think they should try eating at.
Tell your partner about a class you think you should take.
Tell your partner about a class you think they should not take.
What don’t you have to do anymore now that you’re in university?
What do you have to do in university that you never had to do in high school?
What is something you think you must not ever do again?
What is something your parents tell you that you must do?

14. END
Y_T