As an editor I often see these words confused, however, they are not interchangeable. You can’t rely on spell-checker to flag misuse of these words either (unless you’ve made a typo) so it’s important to understand the difference between the two and know when you should use ‘maybe’ and when you should use ‘may be’.
Maybe is an adverb, and it means ‘perhaps‘ or ‘possibly’.
Maybe I’ll start the course in the Summer.
Maybe if I save up I’ll be able to afford a new outfit
Maybe can also be used as a noun and it can mean ‘uncertain’
A good way to test if you’re using the right version when using ‘maybe’ is to replace it with ‘perhaps’. If the sentence still makes sense, you’ve got it right.
Perhaps you could use ‘may be’
May be is a verb phrase. It means something ‘might be’ or ‘could be‘.
I may be tempted to join you for that coffee.
We may be taking on more staff over Christmas.
A good way to test if you’re using the right version when using ‘may be’ is to replace it with ‘might be’. If the sentence still makes sense, you’ve got it right.