Hello, there.
It is very confusing for me the word "Ain't", even some native speakers friends tried to explain me but it is complicated to explain for them. So you have a clear example or explanation?
Hello bro, I guess "Ain't" denies the next word, for example, from Bon Jovi's song
"I ain't gonna be, just a face in the crownd" means "I wont be, just a face in the crownd"
I hope it help you.
Just remember the phrase my grandpa would say: "Ain't ain't a word and I ain't gonna use it!"
But seriously,
Ain't, depending on the context means "am not" or "is not" or some other form of "to be + not".
Hope this helps.