As we reach the semifinals of March Metal Madness 2014, we've now got winners for each of the four regions. Which remaining disc will be crowned the best metal album of the 21st century? That's up for you to decide.

With their 2001 classic, 'Iowa,' Slipknot defeated Iron Maiden's 'Brave New World' in a very tight match. That followed wins over Amon Amarth's 'With Oden on Our Side' and Hatebreed's 'Perseverance.' The Mosh Pit Region-winning album gave us such favorites as ‘The Heretic Anthem,’ ‘Left Behind,’ ‘People = S—,’ ‘My Plague’ and ‘Disasterpiece.’

In the Devil Horn region, Lamb of God's 'Ashes of the Wake' emerged victorious. The band bested Children of Bodom's 'Follow the Reaper,' Black Sabbath's '13' and Gojira's 'From Mars to Sirius' along the way. Their 2004 masterpiece was truly a breakout effort, yielding such standout songs as 'Laid to Rest,' 'Now You've Got Something to Die For,' 'The Faded Line' and the title cut.

Which one of these outstanding discs deserves to compete in the finals of March Metal Madness 2014 to determine the best metal album of the 21st century? Vote for your favorite in the poll below.

(This poll will end on Sunday, March 30 at 11:59 PM EST. Fans are able to vote once per hour, so keep coming back to make sure your favorite album wins!)