Modal verbs in the past
|Modal verbs in the past|
|should be||should have been|
|could be||could have been|
|will be||would be|
|may be||may have been|
|might be||might have been|
|would be||would have been|
Modal verbs – negatives forms
|Modal verbs – negative forms|
|can (used for possibility)
It can happen; everything’s possible.
|can’t / cannot
It can’t happen; it’s impossible.
|can (used for permission)
Can I smoke here? – Yes, you can.
|can’t / cannot / mustn’t
You can’t smoke here. You mustn’t smoke here.
|can (used for ability)
I can play the guitar.
|can’t / cannot
I can’t play the guitar.
|must / have to / has to (used for obligation)
You must be there at 8 o’clock. You have to be there at 8 o’clock.
|don’t have to / needn’t
You don’t have to be there at 8 o’clock.
|must (used for personal opinion, certainty)
He must be here – I can see his car.
He can’t be here – his car’s not outside.
|might / may (used for personal opinion, certainty)
He might/may be late today – there’s a lot of traffic on the roads.
|may not / might not
He might/may not get here on time – there’s a lot of traffic on the roads.
|should (used for weak obligation / advice)
You should stop smoking because it’s unhealthy.
You shouldn’t smoke so much – it’s unhealthy. You shouldn’t spend so much time watching TV.
“Had to” vs. “must have”
The modal verb “must” has two past tense forms: “had to” and “must have”. Which form we use depends on whether we want to express obligation or if we want to say how certain we are about the probability of something happening.
This table below shows us the past tense of “must” and “have to” and when to use them.
|Must / have to|
|When expressing obligation:
I must go. / I have to go.
|When expressing obligation, the past of ‘must’ and ‘have to’ is always ‘had to’:
I had to go.
They had to be there at 2 o’clock.
|When expressing a personal opinion about probability (deduction), we use ‘must’ to express that we feel something is true:
He must be here.
It must be great.
|When expressing a personal opinion in the past, we use ‘must have’, NOT ‘had to’:
He must have been here.
It must have been great.