Heavier? Have you heard the album "transmission"? or even the latest single "Writing's on the Wall"? I'll agree that Metallica is heavy but I've never thought of Creed as heavy. I think of them as mellow and a bit introspective. Mind you I'm only aware of the radio singles (Higher, Arms Wide Open...) and you, possibly, may only be aware of Tea Party's singles (Heaven Coming Down, The Messenger, Walking Wounded)?? The Tea Party really rocks (especially live) and they are definitely heavy.
If you're interested check out the recent concert bootleg "Live at the Dard" available at
http://www.theteaparty.de/english/e_start.htm (for personal use only, of course). It doesn't do much to capture the audience participation (singing, clapping) but I think you'll agree that this isn't exactly easy listening!
I'm going to listen to it again right now, as a matter of fact.
~Willa