I've always imagined the Cacophony, and to some extent Harbingers, very symphonic metal...

The Thorn - http://www.youtube.com/watch?v=tdUB9wr2JCw...feature=related
March of Mephisto - http://www.youtube.com/watch?v=0Qdcl67H1Jw
Ghost Opera - http://www.youtube.com/watch?v=S9hGHnXPEi4

There's something about "The Engine of Transformation"/"Necroscream" that just says "metal".