When do we use Future Simple (will)?
For predictions, decisions, promises and offers
Future Simple with "will" is used for things we decide at the moment of speaking, predictions about the future, promises, and offers. It is one of the most common ways to talk about the future in English!
You decide something right now, at the moment of speaking — not planned before.
I will help you with that!
decided right now
It is cold. I will close the window.
instant decision
I am going to close the window. (planned before)
use "going to" for pre-planned decisions
You think something will happen in the future — based on opinion or evidence.
I think it will rain tomorrow.
opinion about future
She will become a great scientist.
prediction
Look at those clouds — it is going to rain!
"going to" when evidence is visible right now
"Will" is the natural choice for promises and offers.
I will never forget this day. (promise)
promise
I will carry your bag for you. (offer)
offer
Will vs Going to: Use "will" for spontaneous decisions and predictions based on opinion. Use "going to" for plans already decided and predictions based on visible evidence.