Haha, yeah I'm a very rare type of Metalhead, who likes almost everything, I mostly try to be positive in my approach in how I listen to music. There is one subgenre I don't like too much, and that is Black Metal. Yet...there are some bands in Black Metal that I like and tolerate.
The few things I don't appreciate, is extremely hateful lyrics, overly violent lyrics, or sexually explicit lyrics (Which in metal...is a chore sometimes). So that's my only major filter. But other than that, I focus on the musical (Instrumentation,) element first, and if the music resonates, then I usually can get into it.
That being said...A song doesn't have to be technical for me to enjoy it, but it does have to sound "good" and that...is completely subjective, and may even depend on my mood, or if I'm trying to do art, or write story down. It varies.
Feel free to ask me anything on this subject, music is extremely important to me and I like discussing it, even if I disagree, I'll be respectful. Because I know, music is just as important to others as it is to me.