hmm, lemme think...
Graveworm. symphonic black. try the song Demonic Dreams.
possibly Avulsed. the melodies are extremely good, though only some are what people would call EPIC probably. listen to Daddy Stew and Homeless Necrophile
i'll second Amon Amarth (try the song ...and soon the world will cease to be), Emperor, Borknagar although they're not really heavy.
Melechesh. epic (eastern vibed) black thrash. try the songs Covering the Sun and Purifier of the Stars.
Neuraxis. heavy and complex death metal, but subtle melody that is compellingly epic. songs: Structures, Imagery, Reflections. you HAVE to hear this stuff.
Skyfire.....maybe not really heavy (although its fast and the vox are shrieky) but some of the best epic melodies in metal. period.
Some of Zyklon's stuff......