How to Get in Flow When Listening to Music

I was talking with someone, we were talking about productivity and like, how do I get in flow? And I made a comment to someone that like, when I am listening to metal, like I can't listen to any other. It's very hard for me to focus if I'm not listening to metal. Although metal to opera, that is quite a joke. Because I have a little knowledge of opera and they sing a little different than metal singers do. So I think I can kind of relate, but the words thing is what gets me. Any music that has words in it, it's veryhard for me to work with that in the background.