We use I'll ... (= I will) when we've just decided to do something.Appendix 7
B We oft en use I'll in these situations:
Off ering to do something
That bag looks heavy.We do not use the present simple (I do / I go etc.) in these sentences:
I'll phone him now.(not I phone him now)
We oft en use I think I'll ... / I don't think I'll ... :
I'm a little hungry.b: Sure, I'll give it to him when I see him this aft ernoon.I'll help you with it. (not I help)
Agreeing to do something
a: Can you give Tom this book?Promising to do something
Thanks for lending me the money.We use won't to say that somebody refuses to do something:
I've tried to give her advice, but she won't listen.(decided before)
a: I'll meet you at half past ten, OK?When we say 'I'll do something',
we announce our decision:
Oh, I left the door open.I'll go and shut it.
'What would you like to drink?''I'll have orange juice, please.'I'll call him now.'I think I'll have something to eat.I don't think I'll go out tonight.I'll pay you back on Friday.(= the car 'refuses' to start)
Will you (do something)?(not I'll go)
Compare:
I'm meeting Kate tomorrow morning.(= do you want me to open it?)
I've got no money.