Present Form = Past Form

Can = Could

May = Might

Will = Would

Shall = Should

Must = Ought to

lt to offer suggestions or possibility.
Example:
Naruto : I’m having trouble with English.
Sasuke : Why don’t you ask Sakura? Perhaps she could help you.

lt to indicate that the ability existed in the past but doesn’t exist now.
Example:
Hinata : Grandpa, what could you do when you were younger?
Grandpa : When I was younger, I could swim across the big river very well and faster.

lt to express polite requests.
Example:
* Could I borrow your book, please ?
* Could you lend me your cloth now ?
* Could you please close the window ?
* Could you pass the sugar ?

2. Would + Verb base
It for an action that was repeated regularly in the past.
Example:
* When I was a child, I would visit my grandparents every weekend.
* On Sundays, when I was a child, we would all get up early and go fishing.

lt insert rather into the pattern and use this expression to express preferences.
Example:
Neji : What would you rather do in the weekend, go to the party or stay home?
Lee : I would rather go to the party than stay home.

lt to express polite requests.

Example:

Shikamaru : Would you mind cycling with me, Chouji ?

Chouji : No, not at all. It would be nice.

 

lt to give definite advice (advisability). 

Example:

Ino : Tenten, you should study tonight. You will have English test tomorrow, won’t you?

Tenten : I will, Ino.

 

lt to express the subject’s obligation or duty.

Example:

* You should practice for more than an hour. (to musical friend)

* They shouldn’t allow parking here; the street is too narrow.

* Application should be sent before March 25th.

 

lt to tell possibilities. 

Example:

Tsunade : Where is Shino ?

Kurenai : He might be in the studio with Kiba.

 

lt To express polite requests.

Example:

Haku : Might I borrow your coat?

Zabuza : I’m afraid not. It has been brought by Kakashi for weeks and I don’t know when he’ll return it.

 

* To talk about someone's ability (or inability) to do something.

Example:

- "We can find your house without the street plan."

- "She can't have a daughter that old!"

 

* To talk about an action that is necessary (or impossible, or not necessary).

Example:

- "You must always have your driver's licence when you are driving your car."

- "You needn't carry your passport around with you."

 

* To talk about a situation that is possible (or impossible).

Example:

- "Do be careful with that glass, the baby might knock it over"