A lot of death metal is very accessible to people who have previously/also very much been into classic rock or classical music. The music really builds on qualities from these genres, and while DM isn't for everyone by any means, there are a great many people who
could get into it fairly easily.
Only one thing stops them.
The vocals.
Dude, my dad loves half the DM music I put on. He likes the guitars, he thinks the drumming's kinda cool, he likes the complex musicianship and the solos. But like most others, he can't get into it because of the vocals. Most people genuinely just cannot comprehend or appreciate death vocals (high or low) enough to get into the music. To people who are so used to clean vocals, death vocals really do sound completely rediculous. I was one of the lucky people that loved the vocal styles from the start, but my dad.....
there is no salvation for him.
As for emotion.....hmmm. Granted, there's a lot of it in metal, but most of it is negative. Yeah I know, the aggression
purges your own anger and sadness, and that's great, but for appreciating the musical aesthetic itself, metal is by no means the greatest purveyor of positive or ambiguous emotion, or even purely melancholic. It's like, metal is founded from the ethics of anger, chaos, disorder, rebellion which promote a music that initially is geared to sound aggressive and heavy. It's only through evolution of style and taste that it's come to encompass more varieties of emotion, and (to me) these great new emotions in metal other than anger are merely secondary. And, personally, I don't feed from or purge much personal anger nowadays, i'm really only into it for the formal appreciation most of the time. For the greatest powers of emotion, you really can't get more subversice music than classical.
Fucking Death Metal 
