Thread: "Может" vs. "Может быть"

Marcus is right if we speak about "maybe": Может быть, я приду на праздник and может, я приду на праздник are equal. But speaking about "may be"the situation is different.
Example: он может быть учителем
To use может without быть we have to change the noun учителем into the verb учить. Or use another verb instead of быть such as стать.
Он может учить. Он может стать учителем.

In Russian "может" expresses ability (physical or mental) or possibility due to circumstances thus corresponding to the English verb CAN

"может быть" expresses supposition with uncertainty and corresponds to the verb MAY

"Он может прийти" He can come (= He is able to come / It is possible for him to come)

"Может быть, он придет" He may come (I suppose he will come but I am not sure)

"Может" и "может быть" in the latter case may be interchangeable when they are used in colloquial speech. In bookish style only "может быть" is a proper choice.