Heavy Metal Monster?

Well, 1 Thessalonians 5:22 is rather vague. It is probably directed to prophetic utterances in this case (cf. 1 Thess. 5:20). But there is also a general principle that we need to discern all of life in the same way that we discern prophetic utterances. Essentially, this general principle may be summarized as "Don't sin." In any event, this particular verse doesn't really shed any useful light on the question of whether or not a particular song or form of music is evil. It only tells us what to do once we have determined that such a thing is good or evil.

Psalm 101:3-4 is similarly general. It does not tell us how to determine if rock is good or evil. It only tells us how to react once we have made that determination. The encouragement not to set "worthless" or "vile" things before our eyes is an instruction that we are not to heed or to be like those who commit gross sins (e.g., the slanderers and liars mentioned in the rest of the psalm), and that we are not to take pleasure in sin.

Both these passages seem to me to refer to specific sins, as mentioned. But they represent the broader principle that Christians are to live holy, pure lives, and that we are not to commit or to take pleasure in sin.

So, as we consider music of any sort, the point is not that we should not listen to music produced by sinners. The point is that we are not to take pleasure in the sinful aspects of that music, or to be persuaded by them to sin (cf. Rom. 12:2). As I wrote in the answer Rap 'n' Roll, music is usually a mixture of good and bad aspects, just like most other things in life. The Bible does not teach us to avoid all things and people that are infected by sin — to do that we would have to die, because only in heaven does such perfection exist. Rather, it teaches us to be in the world but not of it (cf. 1 Cor. 5:10).

We are to love and fellowship with other people, even though we know that everyone is a sinner, and even though anyone might cause us to sin in some way. On the other hand, we are to avoid those who are likely to cause us to stumble (1 Cor. 15:33). It is a matter of degree, and it is person specific. What causes others to sin may not be what causes you to sin. The point is not to avoid what causes others to sin, but to avoid what is likely to cause you to sin. If you know from experience that your favorite music does not influence you toward sinful thoughts, emotions or behaviors, and that it does not stumble others (1 Cor. 8), then there should be no impediment to you listening to it.

But Scripture does tell us more than, "Don't sin." It also tells us, "Do good" (1 Pet. 3:11). To put it another way, a thing may be permissible but not beneficial or advisable. And again, this is person specific. Perhaps this music benefits you in ways that make it worth your while to listen to it, or perhaps it is merely self-indulgent for you.

My counsel is to use wisdom in evaluating the way you are influenced by this music. Don't be too eager to justify it simply because it brings you pleasure. But also don't gloss over actual benefits and enjoyment it brings you (if any). Things of great beauty and value have been created by evil people for millennia. Benefit from the beauty and value good, but don't fall into the artists' sins.