Hard rock and heavy metal are common terms for broad genres of heavy music. But what is the difference between hard rock and heavy metal?
Perhaps the more relevant question would be: Is there really a difference?
This simple question have two possible answers:
1. No, hard rock and heavy metal are basically different terms for the same kind of music.
This seems to be the answer among at least some fans. This might also make sense considering there are even more terms at hand here: heavy metal, hard rock, heavy rock, heavy music or, simply, metal. They mean more or less the same and we can save time and energy by leaving the issue here.
2. Yes, there is a difference between the two.
The best argument for saying so is linked to the heaviness and darkness of the music. The most important genre traits would thus relate to the amount of distortion on the guitars, choice of notes and the vocal technique used. Basically, heavy metal is more distorted, the choice of notes are rarely blues based and the vocal styles are more aggressive.
If we include non-musical genre traits, heavy metal is very often characterised by a distinct visual image and certain lyrical themes that is more striking than those of hard rock.
Following the first argument, most of the heavy music from the 1970's would thus be considered hard rock. One might, however, argue that Black Sabbath from the early seventies is heavy metal while Deep Purple and Led Zeppelin is hard rock. Later in the decade AC/DC, Aerosmith, Kiss and Van Halen is hard rock while Judas Priest gradually develops into heavy metal.
That said, this explanation is far from waterproof. For instance, what about early Motörhead? Lemmy never accepted that they were a heavy metal band. He was rarely wrong. Some people call Motörhead hard rock. Some call them heavy metal. Some call them speed metal. Adding to that, there was definetaly a good doze of punk running in their veins as well
As the heavy metal genre developped in the eigthees, new genres like thrash metal, death metal and black metal emerged. This evolution established a clear distinction between these new types of extreme metal and the new radio friendly glam metal. The last genre is interesting in this discussion. Some heavier glam metal bands, like Mötley Crüe and W.A.S.P, are generally considered heavy metal. More melodic bands, like Bon Jovi and Europe, are generally considered hard rock.
Since the emergence of more extreme metal genres, the heavyness threshold for being classified as heavy metal has risen. Today, some heavy metal fans will only accept bands with certain extreme genre traits as real heavy metal, leaving many softer sounding bands from the eighties out of their definition of the genre.
Another result ot this musical evolution is the hard rock of the seventies is mostly considered rock today. One fine example is the great AC/DC, whose music won't scare many of today's parents.
So what is the difference between hard rock and heavy metal? It's difficult to conclude but most fans and writers will agree that there is a difference between the two. However, it's not always easy to pin point where exactly that border runs. Any conclusion will also be blurred by another issue: Many hard rock and heavy metal bands have changed their sound during their careers. Hence it might be more fruitful to discuss individual songs and albums rather than bands.
Are the following bands songs hard rock or heavy metal? You decide...
Finally, another relevant question might be: Is this really important? Not really, as long as the metal rocks! Or the rock stays hard. Or stays metal... (Something like that...)
(Thanks to Johannes Støle and Geir Aamo for valuable input on this topic.)