There's a small set of special verbs, called auxiliary or 'helping' verbs. And they come in two types. One type is the 'modal' auxiliaries:
'Mun' is the only one you won't know, and it's an archaic version of 'must'.
Now, almost all non-auxiliary verbs come in five 'shapes', like for instance:
Actually for most verbs the third and forth shapes are the same:
...but about 350 verbs are awkward, including around 100 of the most common. We call these 'irregular' verbs, and they include such everyday actions as 'Drive', 'Give', 'Take', 'Go' and 'Think'. They also include verbs you might never use in conversation, like 'Arise', 'Forsake', 'Forgo', 'Stink and 'Weave'.
But the good news is that the second and fifth shapes are always regularly formed. Number 2 is always number 1 plus '-s' and 5 is always 1 plus '-ing'.
Oh yes, and the forth and fifth shapes aren't actually verbs at all - they're called participles, and they're adjectives. Except they can also be nouns, especially the '-ing' one.
Still with me? Well, none of this is true for the auxiliary verbs.
They have no second ('-s') form. They have no forth or fifth form, so words like 'maying' and 'woulded' don't exist. Three of them (can, will and shall) have third forms for the past tense , but these past forms (could, would and should) also have other meanings of their own - which is why they're listed as separate words.
The other three (may, might, must) have no past tense forms at all, so if you want to shift a sentence like "They might go home" into the past...you can't. You have to say something like "It's possible that they went home".
Another strange thing about modals - they have to be the first verb in a sentence. And that means each sentence can only have one of them, because only one can be first. So sentences like "We might should read more" or "He needed to can speak", aren't allowed.
Oh yes, and you know how you put the word 'to' between verbs if there's more than one of them in a sentence? So you can say things like "She wants to start to learn to drive"? Well you don't put 'to' after a modal verb. Which gives you for instace, "She can start to learn to drive".
Now. There are three non-modal auxiliary verbs. And just to be annoying, they also have separate meanings as perfectly ordinary verbs too.
'Be' is awkward, in that instead of five forms, it's got eight - be, is, am, are, was, were, been, being - and you only get the first one when it isn't the first verb in a sentence. 'Have' has the extra form 'has', used only when the subject noun of a sentence is third-person and singular. And 'do' is the only verb I know of that has an irregular second form - 'does' instead of 'dos'.
Do you remember, way back at the beginning of this essay, I said something about turning statements into questions?
Well, if your statement has an auxiliary verb (modal or non-modal), you turn it into a statement by transposing it with the subject clause.
"I can see you" becomes "Can I see you?". From "People like us will never see his like again" we get "Will people like us never see his like again?".
And "The third kangaroo from the left with the purple hat might possibly be a reincarnation of the emporer's favorite cat, Henry" becomes...."Might he third kangaroo from the left with the purple hat possibly be a reincarnation of the emporer's favorite cat, Henry?"
Which just leaves one small problem. What happens if your statement doesn't have one of these special auxiliary verb things? How can I make a question out of "You love it really"?
Answer...insert an auxilary verb so you can then transpose it! Specifically, insert 'Do'.
"You love it really" becomes "You do love it really", which becomes "Do you love it really?"
As a special extra added bonus, seeing as I'm about to go away for a week's holiday so might not post everyday...some ordinary verbs which aren't auxiliary...but are a bit like them.
They're often called semi-modals, but I'd prefer to call them pseudo-modals.
'Dare' doesn't always separate from other verbs with 'to' - "He dares do things others dare not".
And there's 'ought'. Which can form questions by inversion - "Ought I?" - and only has one form. You can't say "It oughts to be dark by now", or "She's oughting" or "It was always oughted".
It's also the only non-auxiliary verb I know which doesn't have a past form. To put "We ought to go" into the past, you need a different verb, maybe "We had to go".
The next time someone tells you english is a simple, logical language, just point them to this essay.