'will' and 'be going to' which is correct?

Question

I'm not a native-speaker, so sometimes future tense (be going to, will) is tricky to me.

a. If it rains this weekend, I'm gonna stay home.
b. If it rains this weekend, I will stay home.

c. If this happens again, they're gonna lose everything.
d. If this happens again, they will lose everything.

I wrote some sentences with be going to and will. So, which are correct in these sentences? All of them correct or interchangeable? Are some awkward?

Answer 1

Both structures are possible, depending on what you want to say.

Will is used for:

• decisions made at the moment of speaking (e.g. I'll open the door!)
• predictions (I think it will be cold)
• offers or willingness (I will stay at home if it rains - will shows your willingness)
• requests (will you do me a favor?)
• firm intentions, promises (I will always love you)
• threats (I will kill you!)
• facts about the future (Christmas will fall on Monday next year)

To be going to is used for:

• intentions, plans (I'm going to stay at home if it rains)

• saying that something in the future is possible because of something in the present (It's going to snow)

• predictions, especially when there is evidence (this building is going to collapse - it's so old!)