It seems like alot of the good metal shows always happen in Europe, or some Scandinavian country.  Not very many come to the US.  One of my favorite metal bands, In Flames, is headlining Waken Open Air 2012.  Also playing are bands like Opeth, Dimmu Borgir, and the more out of the box Danko Jones. Now the issue of getting myself to Germany....
I have lucked  out on being able to see alot of killer metal bands that have come seperate from the larger tours (just to name a few:  Red Fang, Darkest Hour, Shadows Fall) 
Apart from the well known tours that visit the northwest (Mayhem and Uproar) I have been to 3 awesome metal tours in 2009 in the western part of the US.
Pedal to the Metal- Nothing better than a tour like that coming so close to home! Mudvayne, Black Label Society, Static-X, Suicide Silence, and Bury Your Dead. The only thing that sucked about the lineup is that Dope was originally schedualed to play and dropped off the bill last minute.  Ryan Creek Meadows was packed, beer was abundant, and several of the bands afterward said it was the best stop on tour. 
Summer Slaughter-  While I was acting as a manager for a local metal band, we decided to book some shows out of the state and try to end up in Seattle the same weekend as Summer Slaughter.  We took three days: one night playing a show in Portland, and two nights in Seattle (playing one awesome show with Heiress, and going to Summer Slaughter the next night)  This was mainly a black and death metal lineup and I didnt know of half the bands before hand.  Glad I went, several of those bands have since made it into my personal collection. The ones I knew of were the Darkest Hour, Born of Osiris, Origin, Winds of Plague, and After the Burial.  My awesome finds due to this tour consisted of Blackguard and Ensiferm
Thrash and Burn- I spent a week in Vegas and the highlight of my trip WAS when I got to see Lacuna Coil and Seventh Void at the House of Blues.  What really turned out to be the best part is when I was offered tickets to go to the next show which just happened to be the Thrash and Burn tour headlined by Devil Driver for only $10!  I didnt even know Thrash and Burn was that weekend!  Other bands included Veil of Maya, Periphery, My Children My Bride, Dispised Icon, and a few others. The only suck factor; My PBR was more expensive than my concert ticket.   

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