Subjects exhibiting Metallica Syndrome copies everything the disease's namesake does; build up a huge, devoted fanbase in the mid-80's underground by making fast, heavy, amazing albums, then suddenly fuck over all those true fans by releasing a softer, mainstream,album sometime around 1992-is, a sell-out album.
Later symptoms include earning a huge amount of money and even more fans (mostly weekend headbangers and posers), while abandoning devoted original fanbase, and core values and the style they were famous for in the first place.
More signs bands have Metallica Syndrome include a sudden, sharp increase of the band's attempted publicity, like on TV and the radio, conforming with mainstream music and its neverending attempt to force you to hear their music.
The last and most obvious symptom of the disease is making a 'comeback album', an CD like their 80's albums in style and intensity, basically one that should've been released in place of the shit albums. These albums sell just as well, if not better than their previous tries, and are often critically acclaimed as 'a return' or 'the comeback'. Most of the time, the bands have gone through a shitload of lineup changes and record labels, and don't sound the same, though faggot posers who say they like whatever band argue they do.