WILL is used to talk about:
1) An offer or willingness.
Example:
- I will give you gift tomorrow.
- Don’t be scared! I will be here with until the sun rises.
2) Asking and ordering somebody to do something in the future.
Example:
- Will you be quiet?
- Will you send me some money?
3) Future fact—the action is sure to occur in the future.
Example:
- She will win the beauty contest next week.
- French will lose the football match in the last round.
4) Prediction in the future without evidence.
Example:
- I think it will rain this evening.
- The traffic accidence will take place this morning.
5) Something we decided to do at the moment of speaking.
Example:
A: This box is too heavy!
B: Don’t worry! I will help you.
BE GOING TO is used to talk about:
1) Prediction in the future with evidence.
Example:
- Look! The sky is full of dark clouds. It is going to rain now.
- The battery of this computer is too low. It is going to run out of the electricity now.
2) Something we have already decided to do. (Future plan or arrangement)
Example:
A: What is your purpose to Cambodia?
B: I’m going to visit Angkor Wat.
NOTE: When we talk about things which we have already arranged to do or planned to do in the future, we can use the Present Continuous in stead of Be Going To.
Example:
- I’m having dinner with Zosie at Paramoun Restaurant.
- I’m going to have dinner with Zosie at Paramoun Restaurant.
