The pickup selector position for the neck pickup on a Les Paul is famously labeled "Rhythm", harkening back to a time when the tone of a neck pickup was expected for rhythm work (I guess). Of course, in hard rock and metal it is another story. The bridge pickup seems to be the pickup of choice for aggressive rhythm work. But when did the neck pickup become the stereotypical "lead tone" for metal? You know, that glassy legato tone where the distortion sounds the way really good lube feels. Was there a particular band or metal movement that everyone heard for the first time and then decided to emulate? What is the history of this tonal aesthetic?