We know that 'must' is used to show obligation, deduction,strong recommendation and also for certainty.
She must be going to the market.(certainty/deduction)
He must study to pass the exam.(obligation/strong recommendation)
Now my question is can we use must+V1 to show certainty? For example, if I want to say that Ram is very brilliant boy and it is very certain that he reads all the day , can I say
He must read all the day (to show certainty) ?