I know that some grammar books say that there are a few differences between 'will' and 'going to' in the future tense.
But, do you natives really use it?
Is it worth the effort to think about it during a dynamic conversation?
I'm not sure about this rule but it's something to do with "Was it expected or not what you are about to say?"
Correct me if I am wrong.
Thank you. :)
The Bad News: Yes. There are key differences between 'will' and 'going to'. We also use the present simple and the present countinuous to talk about future events, and also the future continuous, 'will be doing'. And that's before we start on the modal verbs e.g. : 'I may go to the party tonight' 'I might go to the party tonight'. And of course, then there's the future continuous with modal verbs: 'I might be going to the party tonight'. It's subtle and it's complex, and it can't always be explained by grammar books.
A bit more bad news (sorry): There are a lot of misunderstandings around, and misinformation, too. For example, some people will tell you that 'going to' is for the near future and 'will' is for a more distant future. This simply isn't true.
The Good News: It doesn't really matter too much. If you use 'will' all the time, you will be understood. You won't sound like a native speaker - but nobody will misunderstand you, and nobody will be confused or offended if you use the 'wrong' future form.
Sorry, EvanZhang, but that distinction doesn't really work. We can use 'will' when we are very sure indeed about the future. We can use 'will' to contradict an idea, and to insist on the certainty of something. I can do this, and I will do this.
One of the easiest things that an English learner can do to sound more native is to use contractions most of the time and only separate these words for emphasis. For example
"I'll" instead of "I will"
I'd... I would
I'm... I am
it's... it is
I've... I have (as a helper verb, not its possessive form)
It's all instinct! That's why the majority of native speakers don't have any idea how to explain why we use one form as opposed to another. We instinctively know what sounds right. There are no actual rules to learn when it comes to future forms, and some people claim that English doesn't really have a future tense, as such. There are just various modal forms (will, may, might etc) which indicate a degree of certainty, plus certain idiomatic phrases such as 'I'm going to' and 'I'm about to'.
In fact, other than a few spelling rules, we don't really learn anything about the English language at school.
But if you want one very common distinction between 'will' and 'going to', take a look at my answer here:
I don't think that natives give it much thought... I'm going to the bar tonight, are you coming? I will be there. I'm going too! I'm there. I would be going but I have something else that I have to do. I will try to make it. I was there last night and will go back next week but I won't be able to go tonight.
I'm sure there are reaons why you would say "I am going" vs. "I will go" or "I will be going" but they all sound fine to me.