Welcome brother.
First off, thank you for welcoming me on the forum.
Second, I would like to address this by paragraph, so bear with me!
My reason for liking black metal? It promotes independence and free thinking! I would of never of considered Islam if it was not for black metal! To think for myself, aside from what western media portrays muslims as could not of been done without some kind of free thought. And I do not think they are atheist or even believe the lyrics they are saying - many pretend satanism (very well, actually) But just to keep the music underground. Again, it values independence and free thinking. Something I think every muslim enjoys - the greatest gift of man is to Reason. With Reason, he can see Allah exists. He can also see due to limited circumstance that Allah may not exist, but this is just a reasoning error, if thought upon too hard, he will see the fault in it.
As for functioning in the army, how is that an issue? I know plenty of soldiers who enjoy metal, including the black variety. The lyrics again, aim more at overcoming ones obstacles, and being free. For example, take Gaahl of Gorgoroth, or Varg Vikernes of Burzum - they may sound "satanic" but at least one of them is Pagan. It is the same with many bands. They use the name of Satanism in the general sense of one who opposes christanity, and not logic and reason. In fact, to say that any human is a son of god is ridiculous - even you can agree to that. Again, Satan is just an image of Arche-type of freedom from notions, reasoning for oneself, and thinking of everything one has learned anew. Something that christanity does not allow - but Islam, as far as I can tell, does.
Again, blaming Funeral Doom for your depression is not quite correct - I daresay, for people who actually like the music and play it, hearing it is a relief - they know that they can let that emotion out and move on. That is how it is for me - I am lightened when I hear the music because I know someone else feels the same way.
I mean NO disrespect in the above, and is simply my viewpoint. I would like to add that I am not muslim, but I am trying to use my God-given sense of reason to reach a point of logic.