Writeacher, I downloaded a few details about modals expressing possibility/probability but I'm still doubtful about their use. My questions to you are numbers 1-2.
Using modals to talk about the present:
1)Will / won't
We use will and won’t when we are very sure:
•She’ll be at work now.
2)must / might / could / may / can't
•She must be on the bus. (I'm fairly sure this is a good guess)
•She might come soon. (maybe)
•She could be lost. (maybe)
•She may be in the wrong room. (maybe)
•She can’t be at home. (I'm fairly sure this isn't true)
1) Do might/could/may have exactly the same meaning?
2) How would you express the same sentences in the past?
She must have been on the bus.
She might have come soon.
She could have been lost.
She may have been in the wrong room.
She can't have been at home.