Will and be going to are both forms of the Future Simple tense. ESL and EFL students need to be taught both forms.
The more difficult part for students is knowing when to use "will" and when to use "be going to" to express the future.
Conjugating the Future tense is fairly easy.
The use of "will" is conjugated with this straight-forward formula:
For example, "She will arrive at 9 p.m."
See my Future Simple Tenses page for a thorough discussion of all the forms of this tense.
"Be going to" is conjugated this way:
Using "Will" or "Be Going To
So when do you use "be going to" and when do you use "will"?
They both have the function of being used to talk about something in the future, but there is sometimes a subtle difference between the two. This subtle difference can be difficult for ESL and EFL students to distinguish.
Here are the general rules for will and be going to:
(1) Predictions: Both will and be going to can be used to make predictions about the future.
Weather predictions are the easiest examples for students to understand.
The weather channel said it will rain tomorrow.
Don't cheat. You'll get caught.
(2) Prior Plans: "Be going to" is used to express plans previously made for the future.
You cannot use "will" for this purpose.
She's going to take a vacation this summer.
We're going to go to the library tonight to study.
(3) Willingness: "Will" is used to describe willingness to do something.
"Will" and "be going to" are both used to talk about the future. When students are not sure, the default tends to be to always use "will."
I've noticed that the problem area tends to be when talking about prior plans. The correct form of the Simple Future is "be going to," but students tend to use "will" because they are more familiar with this form of the Future tense.
And as with most English grammar points, it takes a while for students to get the hang of it when speaking. Again, the default tends to be to always use "will."
Drills asking students questions about the near and distant
future in their lives will help to reinforce when to use "will" and "be