And what then is solution for people who listen only to metal? And have never heard about or considered believing in God? You don't think it could be used as a gateway?
Hello Hannahbeth; thanks for your question.
For those who listen only to metal music; and who have never heard about God, i believe the solution is simply sharing with them the Gospel of Christ. Afterall; it is the Gospel which is the power of God unto salvation (Rom. 1:16).
And in the Bible; music is never used as a tool for evangelism. The Gospel is always the bridge in reaching the lost. And so that is my answer. Just give them the Gospel.