Teen-agers, the band's primary audience, are grappling with the fact of mortality, and Slayer shares that fascination. When Mr. Araya isn't singing about blood rituals and psychotic rampages, he's detailing the ravages of war in songs like ''Mandatory Suicide,'' ''Chemical Warfare'' and ''Behind the Crooked Cross,'' which Mr. Araya introduced by asking, ''Do you think you should have a right to choose whether to live or die?'' The force of the music, and its desperate urgency, exorcise genuine fears.

The music's aggressiveness does hurl a crowd into motion, and the Felt Forum audience was by no means decorous. After the mediocre opening band, Danzig, there was a long delay as people on the floor, where seats had been removed, were asked to move back so a barricade and monitor equipment could be set up. A line of policemen with nightsticks came onstage to back up the request.

During Slayer's set, there were pockets of slam-dancing on the floor; up front, audience members continually climbed onstage to launch themselves into the audience. Slayer performed amid a line of bouncers who kept the stage-divers away from the band. It was easy to tell which of the band's guitarists, Jeff Hanneman or Kerry King, was playing a solo: he would stand back from the rumpus to concentrate on his fingers. In the latter part of the show, cushions torn out of the seats in the stands started flying through the air; a Felt Forum spokeswoman estimated a few thousand dollars in damage. There were no arrests or medical emergencies.

''You guys came here to have a good time, and you're blowin' it, big time,'' Mr. Araya complained, dismayed by the melee. ''Why don't you give us a break? We can probably never play here again.'' And then the band played ''Angel of Death.''