I might/may go if he calls me.

[wrongnumber]

The following content is from the Farlex's Complete English Grammar Rules:

"I might go if he calls me. (Might expresses a 50% possibility.)"
"I may go if he calls me. (May is similar to might, but it is more formal and the possibility is slightly less.)"

My questions are:
Does might mean it can be likely to happen? The possibility is higher than sometimes, right?
Doesn't may express more posssibility than might?

 

[emsr2d2]

The following content is from the "Farlex's Complete English Grammar Rules":

"I might go if he calls me. (Might expresses a 50% possibility.)"
"I may go if he calls me. ("May" is similar to "might", but it is more formal and the possibility is slightly less.)"

My questions are:
1. Does "might" mean it can be is likely to happen? The possibility is higher than sometimes, right?
2. Doesn't "may" express more possibility than might?

Note my changes above.

1. The book you've quoted is clear - it claims it expresses a 50% possibility. Therefore, you can't say that it's "likely to happen". It's just as likely to happen as it is to not happen. (Note that I disagree with this "50%" claim.)
2. Are you saying that you think the opposite of what the book says?

I warn you that you're not going to get a definitive answer on this from any native speaker. This alleged distinction between "may" and "might" has been discussed countless times and we always end up with the same result - there is no straight answer. You can't attach percentages to these words - this is English, not mathematics.

 

[wrongnumber]

2. Are you saying that you think the opposite of what the book says?

Yes, I think the opposite of what the book says because "might" suggests less definite than "may", right ?

 

[5jj]

emsr2d2 has already said:

I warn you that you're not going to get a definitive answer on this from any native speaker. This alleged distinction between "may" and "might" has been discussed countless times and we always end up with the same result - there is no straight answer.

 

[wrongnumber]

esmsr2d2 has already said:

But I just can't understand why the book says the possibility of may in the second sentence is slightly less .

So these two have little difference in meaning?
I might go if he calls me.
I may go if he calls me.

 

[5jj]

That book is not one I would recommend to any serious student of English grammar.

 

[Tarheel]

But I just can't understand why the book says the possibility of may in the second sentence is slightly less .

So these two have little difference in meaning?
I might go if he calls me.
I may go if he calls me.

I can't explain to you why the book says what it says. As for those usages, the difference is subtle and not, I think, worth worrying about. If there is any difference in meaning it depends on context. (My opinion.)