OK. Try to hear some.....
Dream Theater (progressive metal. Medium heavy. Epic songs, many rolling in over 10 minutes long)
Lamb Of God (Speed metal with melody, not just a wall of noise. Best album is 'Sacrament').
Meshuggah (Not particularly fast, but as heavy as non death-metal/doom-metal gets. Progressive in a new way. Try to hear 'Bleed' or 'Combustion' on Youtube). May be a step too far for you though.
Tool. Very, very good band. hard rock/softer metal with brains and feeling. Check out their album 'Lateralus'.
Devin Townsend. His album 'Terria' is a hidden gem. Those not in the know are missing out. I'd say BUY IT NOW! Has the added bonus of being produced very, very well.
Strapping Young Lad. Devin Townsend's old band. Pure, brutal, speed metal. A tad 2 dimensional, but perfect for those times when nothing else will do.
Fear Factory. Awesomely good industrial thrash type stuff. Try 'Obsolete' or their latest album 'Mechanize'.
Those will get you started. If you report back with the stuff you liked and the stuff you didn't, it'll give me a greater idea of other stuff to recommend to you. Youtube is a great resource for finding new bands.