One thing I have noticed over the last 15 years as a metal enthusiast is that my concept of "heavy music" has changed significantly. I used to think it didn't get any "heavier" than Soundgarden, The Smashing Pumpkins and Metallica. These particular bands had songs that were fast, aggressive, and had maniac drummers to keep the beat. Now, keep in mind that I started listening to "heavy" music when I was 9 or 10 years old (1995, 1996). At one point in time I didn't think music could get any "heavier" than these songs:
"Tales From The Scorched Earth" by The Smashing Pumpkins
"4th of July" by Soundgarden
"Until It Sleeps" by Metallica
I still love loud, distorted, chunky guitars, and a pounding rhythm sections to drive song. Bands like Deftones, Korn, and Slipknot helped evolve my concept of what "heavy" music was and could be. If a song had enough energy and aggression in it that I wanted to get in a mosh pit immediately, then that was what I called "heavy."
When I decided to pick up the guitar I wanted to learn how heavy bands got their sound. What does "heavy" mean anyway? After researching the topic for a while I have found out that there is not exact formula for achieving a heavy sound. However, there are several elements that can give a song "heavy" feel to it.
For guitarists this includes but is not limited to:
1) Power chords
2) Pick Attack
3) Palm Muting
5) Heavy Distortion
The rest of the band can make a song heavy too by utilizing:
1) A drummer who knows when to add a kick drum on particular downbeats to make a song "punchier." Metal drummers will often use (and overuse) double-kick pedals to add a sense of chaos to an arrangement.
2) A bassist who locks in with the guitar and essentially plays the same part, perhaps even an octave lower
3) A vocalist who can write intense lyrics and perhaps scream, growl, or match their lyrics with an equally intense delivery