Use must for a strong deduction, might or may for a possibility, and can’t for a deduction that something is impossible. These forms show the speaker’s confidence, not guaranteed facts.
Practical examples
She might be in another meeting.
ربما تكون في اجتماع آخر.
He must be tired after that journey.
لا بد أنه متعب بعد تلك الرحلة.
That cannot be the final version; it has no title.
لا يمكن أن تكون هذه النسخة النهائية؛ ليس لها عنوان.