In our quest to find the greatest metal album of the 21st century so far, we're finally down to the final four recordings! Both of these records deserve a spot in this latest battle, as each act has achieved monumental success through both mainstream popularity and genuine innovation.

Tool have made it to the semifinals with their 2001 masterpiece, 'Lateralus.' In Round 1 of March Metal Madness 2014, 'Lateralus' bested Cynic's 'Traced in Air' by a substantial margin. Tool moved on to face Cannibal Corpse's 'Kill,' attaining another win before defeating the mighty Pantera and their sole 21st century full-length, 'Reinventing the Steel.'

System of a Down sport an impressive winning streak as well in March Metal Madness 2014. Their 2001 breakout album, 'Toxicity,' took down Ghost's 2013 breakout record, 'Infestissumam,' in Round 1. 'Toxicity' continued its journey by squaring off with Opeth's masterful 'Blackwater Park' before driving the nails into Slayer's 'God Hates Us All.'

Will Tool's 'Lateralus' make it to the Final Round? Or can System of a Down emerge victorious in this incredibly tough battle? Your votes will decide. Choose your favorite 21st century album in the poll below!

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