Thrash Metal is a music genre not known for its subtlty. The Texas heavy metal band Pantera, 1981-2003, was perhaps the epitome of the thrash metal style. With its pounding beats and screaming double-time guitar riffs, thrash is meant for the mosh pit, not so much a form of slam "dancing" as a militaristic pagan ritual that entrains the mind and evokes an adrenaline and testosterone pumped berserker rage.
The berserker is known to us primarily from Norse history and anthropology. Members of the bear cult, such men danced in bearskins, and showed the bears sometimes placid, sometimes ferocious nature. The phenomenon of the sometimes warrior, the taciturn male who might spend months in becalmed isolation, hunting or fishing in the frozen north, only to release his fury in a violent fit is known throughout the Arctic among tribes as far east as the Eskimo. In prehistoric times the herdsman and hunter gatherers of the north led a hard life, fighting against the elements with wits and patience. War was seldom and costly. But when the need came to defend oneself, the stolid laborer could transform into the berserker. This was originally brought on by stress, but often came to be institutionalized, encouraged by the use of Amanita mushrooms or by cultic dances. The Byzantines remarked upon a "Gothic dance" performed by the emperor's Varangian guard. An animalistic mode of mind meant for individual combat, where a man had to quickly overcome his inhibitions to meet a sudden threat, had evolved on the edge of civilization to a cult seen as useful to the military leader, but also a threat, a double-edged sword that was eventually outlawed as the berserker peoples were Christianized.
The berserker phenomenon is obviously a relic of our animalistic past. As a fighting form, the mad warrior who fights in the nude without regard to personal safety will not prevail against the calculating and disciplined troops of Rome or the US Marines. But whether we see it in the movie Fight Club or in the thrash metal mosh pit, the berserker phenomenon is still a part of the male nature. Initiating physical violence against the innocent may be wrong, but boxing and wrestling and the physical contact of American football feels good. And if it can be expressed in a sublimated form, it can be a thrilling and even addictive experience.Slam dancing is one such sublimation. The "moshers" or slam dancers assemble in an enclosed area tightly packed mostly with young men. Suitable music is played with a beat conducive to bouncing up and down on two feet. The dancers bounce off each other and the walls, building into a frenzy. People swing their arms and twirl about like dervishes or ball-bearings in a shaken can. The beat of the music induces a trance. The release of adrenaline induces a state of euphoria. There is physical violence although not individual malice. People do get punched by flailing fists. There are falls and bruises and broken bones, and some have broken their necks.
Stage divers leap from the stage onto the awaiting arms of the crowd, who buoy the divers up and pass them along in what looks like a parody of a trust-building exercise at a motivational camp. Yet this is the real thing, not a parody. Evereyone is here voluntarily, enjoying the same music, engaging in what is not an act of malice but more a team sport or a pagan ritual. Afterwards there are smiles and sweating bodies that remind one of an athletic meet, not a gang fight. Young men have enjoyed their animal natures in a freely organized forum with a joyous physical lust that borders on the erotic. The psychic power manifested here is certainly of a kind with that which in malevolent circumstance and under the control of a demagogue will become a Nazi or Jihadist or Kamikaze rally. Used properly, the mosh pit is no more questionable than the shooting range or the boxing ring. It is not the expression, but the use and purpose that determines the morality of the action.
Here is Pantera, perhaps the premier thrash metal group of the 1990's, performing "Walk" in their tour with White Zombie. You can see stage divers in the front of the crowd, but the slam dancers are back from the stage by about 30 feet.
Little compares to Ludwig van Beethoven. One of the strangest opinions I've ever heard of Beethoven is that his music is malevolent. He certainly can convey darker themes with his compositions. The Fifth Symphony, with its "Fate knocking at the door" is far from lighthearted. Indeed, Beethoven can be seen as the first Heavy Metal artist, with the booming epic style of his symphonies. Considered a member of the Classical school along with Mozart and Haydn we can hear echoes of Shubert and a foretaste of the Romantics that is absent mostly, say, in Mozart. To make a grossly inadequate analogy for the student of pop music, Beethoven's dramatic range is like Led Zepellin to Mozart's saccharine early Beatles.
One of my favorite of all classical pieces is Beethoven's Sixth Symphony, "The Pastoral." Composed, rehearsed and debuted along with the more ominous Fifth, The Sixth, with its buoyant mood, provides a perfect complement. The Pastoral Symphony, which is intentionally meant to evoke "recollections of country life" has been famously adapted to two iconic movies of the Twentieth Century. The first is Walt Disney's animated masterpiece Fantasia. The full five movements, performed by Leopold Stokowski directing the Philadelphia Symphony Orchestra, are illustrated with scenes of Greek and European mythology that comprise one of my earliest and most joyful childhood memories. 
The second iconic film usage is in 1973's sci-fi noir, Soylent Green. The fatherly police archivist Sol Roth, (Edward G. Robinson in his last role,) has watched America decay from greatness to mindless rioting and self-delusion. Choosing to die, he patronizes a state-run euthansia clinic. With all the world's wildlife dead, Roth watches images of the countryside and listens to Beethoven's Pastoral as the fatal cocktail takes effect. Of course its use in Soylent Green is darkly ironic. The piece itself conjures no malevolent images, at least nothing worse than a soon-passed summer thunderstorm. 
