You could talk about the term, "heavy metal" itself - it actually comes from a Beat Movement Novel, Naked Lunch by William Burroughs. Perhaps you could find a synopsis of the novel (or read it, if you've got the time!) and link the heavy metal thing to the significance of the Beat Movement. I recently did an assignment on Operation: Mindcrime by Queensryche, talking about how it was essentially a denunciation of the Conservative Protestant political and religious establishment in 1980s America. And, perhaps it's more of a sociological thing, but you could talk about how all the tribute merchandise that's come out since the death of Dimebag Darrell is indicative of pervasive commercialism in the arts in America, to the point where the alternative/underground music scene is exploited for its commercial value (could also refer to the nineties death metal boom for this).