English grammar : should/must(not)

Must 

1.obligation 

 you must obey the law
 you must pay the bill at once
Everyone must bring one dish
You must fire them for the sake of your team.

2.high possibility

 you worked so hard all day. you must be tired.
 This is a new model of i phone. it must be expensive.
 You must not have slept well recent days

should 

1.obligation 

You should not be rude to anyone.
Should she see a doctor?
What time should we come to your house?
What should we bring?

2.expectation/suggestion

It should rain heavily tomorrow, according to the weather forecast.
she doesn't like her new job. she should look for a new one.
You should stop thinking about him.


*obligation 
The difference between should and must obligation is that 'must' is stronger.

Rephrasing Sentences

Rephrase the sentences below using must or should

1. Don't play with fire!
 = you must not play with fire!

 2. I suggest going to bed earlier.
 = you should go to bed earlier.

 
 3. She is probably tired.
 = she should be tired.

 4. It will probably be sunny tomorrow.
 = It should be sunny tomorrow.

 5. Don't go to the party.
 =You must not go to the party.

 6. I suggest not going to the party.
 = You should not go to the party.

Sentence Building

Tell a child the things they should/must or should not/must not do.

tell the truth → "You should tell the truth!"
clean up your toys  → You should clean up your toys
clean your room  →You must clean your room *by yourself.
 by yourself / on your own
brush your teeth → You should brush your teeth
get up now → you must get up now, you are already late.
make your bed → You should make your bed
be late → you must not be late
wear a coat → you should wear a coat
eat your breakfast → you shouldn't eat too much breakfast
be polite → you should be polite
share your things → you must not share your things
eat with your mouth open → you should not eat with your mouth open