A future tense (/ˈfju:ʧə(r) ˈtens/) is a tense found in some languages.
English only has two tenses (present tense and past tense) and lacks such a future tense. Rather, future time is expressed by using either of the English tenses, i.e. the present tense or the past tense. Note time–tense distinction.
Despite this, some pedagogic grammar analyses include an English “future tense.” What they generally mean by this is the full modal verb will used to express the future.
However, they also may refer to other modal verbs (may, shall, can and must can also be used for future time). They also may refer to the semi-modal verb going to.
Instead of teaching students the lie that there is a future tense, it may be a better idea to teach them the truth, and just focus on structures with will in appropriate context.