Talking about complete possibility
The auxiliary verbs that can be used to express complete certainty are shall, will, can, could and must.
- There is the phone. That will be Ram.
- I shall come tomorrow. OR I will come tomorrow. (Both shall and will can be used with I and we. There is no difference in meaning.)
- He will come.
- It will rain this evening.
- It won’t rain this evening.
- There is the doorbell. Who can it be? Well it can’t be James – He is in Delhi.
- You must be tired. I will get you something to drink.
- I will buy a car if I get my rise.
- She will come if you invite her.
Expressing probability and possibility
We can use the auxiliary verbs should, ought, may and might to talk about possibility and probability.
- She should be here soon.
- She may come.
- It may rain this evening.
- We may go camping next week.
- She ought to know better.
- I may buy a car.
- You should be able to solve the problem.
- She may buy that house.
- I should be able to finish this job by Monday.
Might shows less possibility than may.
- She might come. (Perhaps a 20% chance)
- She may come. (Perhaps a 50% chance)