Will and Shall

 Will

We use will to say what we know or think about the future.We use will when we have just decided to do something.

What would you like to drink? I will have an apple juice,please.

I will call you when I arrive.

I feel a bit hungry. I think I'll have something to eat.

Jack won't pass the exam. He hasn't studied hard enough.

Offers and suggestions:

 I will help you with your chemistry homework, if you like.

I will carry your bags.

Will you join us for lunch?

Requests:  

 Will you please turn off the music?

Marry, will you do me a favor?

 Shall

We use shall only with I and we. Shall is a little more formal.

We can use shall for the future

I shall be on holiday in April.

We shall probably go to France in June.

Shall is used mostly in the questions shall I ... ?  shall we ... ?

 Shall I open the window? (=Do you want me to open the window?)

Shall we go? Just a minute. I'm not ready yet.