"Maybe" is an adverb. "May be" is just two verbs. You may use "may" with any other verb to indicate a possibility of something happening, like I did at the beginning of this sentence. Ex. "Maybe I will go there tomorrow." "Maybe that's right, maybe it's not." If a sentence has "maybe" and a form of "to be", you can usually rewrite it as "may be". Ex. "Maybe that's right" = "That may be right" There's a very subtle difference in tone between the two, but I can't put my finger on it. They just sound different, but they really mean the same thing. It's not technically wrong to say "Maybe that may be...", but it's redundant. It sounds very awkward. A lot of native speakers mistakenly write "may be" as maybe. In spoken language the pronunciation is exactly the same, but when you're writing you need to decide if you're using an adverb or two verbs.

maybe+sentence(another verb)because it is adverb but (may be+adjective)because it is a verb(and verb to be need adj.)