Can I use them for Future tense? For example
"I must/may/might go to New York tomorrow".
and can they be used in Present continuous form as well? For example
”He must/may/might be having dinner”.
I tried to look it up on Google but couldn't find any thing relevant. So any help would be greatly appreciated.
Can I use them for Future tense?
Yes.
and can they be used in Present continuous form as well?
Yes.
"Both may and might can be used in requests and in expressions of possibility for the present and future." https://grammar.collinsdictionary.com/us/easy-learning/may-and-might
Research indicates that "might" is the simple past form of "may", however they are used interchangeably these days, "might" is no longer strictly a past tense form.
Either "might" or "may" may indicate uncertainty and expressions of possibility for the present or future.
He might be reading. (possible event in the present)
He might go tomorrow. (possible event in the future)
Next, "must" is a present tense form indicating a necessity to do something in the present.
He must study now.
The future tense would be "will have to". Yet, you can still say:
He must go tomorrow.
This is a necessity (in the present) regarding an action (in the future).
Moreover, the present tense can be one of several ways we talk about the future in English.
"When we know about the future we normally use the present tense."
https://learnenglish.britishcouncil.org/english-grammar/talking-about-future
Thus, "must" can in practice be applied to present and future-related sentences.
