Usage of "ain't" in formal conversation
Solution 1:
No, it is not the ideal phrase for a formal conversation. Maybe in commercials, music etc. but not in formal usage between someone you don't know. I mean if you use it in a supermarket it is OK, but kind of weird during a job interview or when talking with a doctor or somebody who you want to show some respect. But I will use it in marketing, commercials, music and stuff of that sort.