Modals to express degrees of certainty

1. MODALS TO EXPRESS
DEGREES OF CERTAINTY
Grammar Explanation

2. SPECULATIONS ABOUT THE PRESENT
Affirmative Negative
It must be true. It can’t be true.
has to couldn’t
has got to must not
Affirmative Negative
It may be true. It may not be true.
might might not

3. SPECULATIONS ABOUT THE PAST
Affirmative Negative
It must have been true. It can’t have been true.
had to have couldn’t have
has got to must not have
Affirmative Negative
It may have been true. It may not have been true.
might have might not
could have

4. SPECULATIONS ABOUT THE FUTURE
Affirmative Negative
We should solve it soon.
ought to
Affirmative Negative
We may solve it soon. We may not solve it
soon.might might not
could