Modal verbs Level of probability

Look at this chart to see different levels of probability and modal verbs used

MODAL VERBS USED TO SHOW LEVELS OF PROBABILITY

LEVEL OF PROBABILITY	MODAL VERB	TIME = PRESENT & FUTURE	TIME = PAST
CERTAINTY	WILL (Be)	He'll be here by Friday.	That will / would have been Susan who called.
CERTAINTY	WON'T (Be)	She won't be here.	It won't / wouldn't have been John, I think he's in São Paulo.
IMPOSSIBILITY	CAN'T Be COULDN'T Be	It can't be Fred, he's in the USA. It couldn't be right.	He can't / couldn't have written this, he doesn't speak Arabic.
PROBABILITY (LOGICAL)	MUST (Be)	He must be right, he's an expert in this area.	He must have finished by now, he's a fast worker.
PROBABILITY (LOGICAL + PREFERENCE)	SHOULD (Be)	He should be finishing now, he's a fast worker.	He should have finished by now, the exam's nearly over.
POSSIBILITY	MIGHT (Be)	They might win, but I doubt it.	If they had played better, they might have won.
POSSIBILITY	MIGHT NOT (Be)	It's very cloudy, but I might not rain.	If I hadn't read that book I might not have passed the exam.
POSSIBILITY	MAY (Be)	We may go to Greece for our holidays.	She may have got lost.
POSSIBILITY	MAY NOT (Be)	I may not arrive on time.	He may not have done it.
POSSIBILITY	COULD (Be)	You could be right, but I doubt it.	He could have had an accident even though he's a very good driver.

MODAL VERBS USED TO PERFORM SPECIFIC FUNCTIONS

FUNCTION	MODAL VERB	TIME = PRESENT& FUTURE	TIME = PAST
COMPULSION	MAKE SB (Do)	She makes them tidy their room.	The teacher made them write it out six times.
PROHIBITION	CAN'T/NOT ALLOWED TO	My dad says that I can't see you anymore.	She wasn't allowed to see him anymore.
PERMISSION	MAY (Be)	May I go now?	I was allowed to go.
STRONG OBLIGATION	MUST (Do)	I must remember to pay the phone bill.	I had to apologize.
STRONG OBLIGATION	MUSTN'T (Do)	Mother: "you mustn't play with matches."	The children weren't allowed to play outside.
NO OBLIGATION	DON'T HAVE TO (Do)	I don't have to wake up early on Saturdays.	I was happy that I didn't have to see him again.
NO OBLIGATION	NEEDN'T (Do)	You needn't pay it now if you don't want to.	You needn't have done it, but I'm glad you did.
NO OBLIGATION	DON'T NEED TO (Do)	I don't need to study French anymore.	He didn't need to revise for the exam.
DUTY	SUPPOSED TO	Your supposed to arrive at work at 8am.	You were supposed to have done this by now.
DUTY	NOT SUPPOSED TO	You not supposed to be here!	I wasn't supposed to have been at the meeting.
FORMAL ADVICE	WOULD (Do)	I'd arrive on time if I were you.	I would have arrived on time if I'd been him.
FORMAL ADVICE	WOULDN'T (Do)	I wouldn't do that if I were you.	I wouldn't have done that if I'd been him.
INFORMAL ADVICE	SHOULD (Do)	You should always dress well at interviews.	You should have dressed well at the interview.
INFORMAL ADVICE	SHOULDN'T (Do)	You shouldn't speak to him like that.	You shouldn't have spoken to him like that.
INFORMAL ADVICE	OUGHT TO (Do)	You ought to be here earlier.	You ought to have been there earlier.
INFORMAL ADVICE	NOT OUGHT TO (Do)	You didn't ought to touch that.	You didn't ought to have done that.
REQUESTS	CAN (I/you)	Can/Could you help me, please?	I asked him to help me.
ABILITY	CAN (Do)	I can speak English.	I could speak English when I was five.
ABILITY	BE ABLE TO (Do)	Will you be able to come?	She was able to answer all the questions.
ABILITY	MANAGE TO (Do)	Does he manage to get here on time?	He managed to rescue her.
NORMAL BEHAVIOUR	WILL	She'll always do her homework.	She would always do her homework.
OFFERS	WILL	I'll help you with that.	I'd have helped you.
OFFERS	SHALL	Shall I give you a hand.	I should have helped you.
SUGGESTIONS	SHALL (LET'S)	Shall we meet at 9pm?	I suggested meeting at 9.
WILLINGNESS	WON'T (Do)	I won't do it!	She wouldn't do it.