The teaching of English is seriously damaged by trying to fit it into a \latin mold, that could hardly fit it worse. Before I launch into this, let me observe that “aller”" in French functions exactly as “going to” in English and is the most common form of expressing future.
The most important observation is that the English verb form does not express tense. What it expresses is “aspect”. There are two forms, the imperfect, mistakenly called the present and the perfect, generally called the past. As an example, consider the sentence, “I go to my office every day.” The idea it expresses is simultaneously past, present, and future. Contrast, “I went to my office every day (until I retired).” past action, to be sure, but mainly completed action (prefective). The main constrast in meaning between “Jon has been a mathematician” and “Jon was a mathematician” is that the second has an implication that Jon is dead. I could go on with this a long time, but I desist.
Another observation about English is that while many languages have modal verbs, English has a part of speech called modals. But their grammar differs sufficiently from that of verbs that it is best to consider them a distinct part of speech. There are several ways to recognize the difference. First place they cannot be governed by modals. In German you can say, “Ich mussen koennen machen etwas” and in French, “Je doit pouvior faire quellque chose”, but in English you must say something like “I must be able to do something”". Second, only “be”, “do”, and modals can be used in questions and negatives without “do supposrt”. (Sometimes “have” can be so used but that usage is becoming increasingly archaic.) Thirdly, along with “do”, “be”, and “have”, they can govern a verb without a preposition. Interestingly, the optional modals “dare” and “need” can be used both ways, but can be inverted and negated only if used without “to”.
Apparently the modals were verbs until about 1550. In the ensuing 50 years, they ceased being verbs and the periphrastic constructions, “be going to”, “be about to”, “be able to”, “have to”, entered the language.
This and much more can be found in a book called “Prncipals of Diachronic Syntax” by David Lightfoot, where I learned it. He gives much better arguments than I can.
I think the teaching of ESL would be vastly improved if the actual grammar of English were taught and they stopped trying to shoehorn into a Latin mold. Just the distinction between perfect and imperfect might go a long way to sorting out the question of when to use the so-called progressive forms that give non-native speakers such problems.
A native German speaking colleague of mine told that he once spent a sleepless night before he realized the simple rule that determines whether a German verb uses a “ge-” prefix in the past participle. The rule is not taught to students learning German (wasn’t to me) and, while known unconsciously to all native speakers of German, had never been articulated before as far as he was aware:
The “ge-” is used in the past participle if and only if the verb is stressed on its first syllable.
