The Future
Will/Shall
When we give information about the future or predict future events that are not certain we usually use shall/will.
For example:- Q) Who do you think will win the election?" A) "I'm not sure but I think the current party will win."
We can also use shall/will to make promises for the future.
When leaving work I would say - "Goodnight, I'll (I will) see you tomorrow."
Shall/Will is often used when we just decide to do something.
For example:- The phone is ringing - If I decide to answer the phone I would say - "I'll (I will) get it."
It can also be used in formal situations to express planned events and is preferred in formal written English.
For example:- The party will start at 10.00pm. -
To Be Going to
We say something is going to happen when it has already been planned.
For example:- Q) Are you going to fly to Germansy? A) No, we're going to drive.
We also use it to show something has already been decided.
For example:- "We're going to buy a new car next year."
We also use going to when we can see something is about to happen.
For example:- "Look at that cloud. I think it's going to rain." and "Watch out! He's going to crash into that tree!"
Present Simple
When something is arranged according to a fixed schedule we use the Present Simple to talk about the future.
For example: -"The plane lands at six o'clock."
Present Continuous
When you plan to do something in the near future (in a couple of days) you can use the Present Continuous.
for example: -"We are meeting him this afternoon."