The first round of MTV's Musical March Madness tournament comes to a close on Monday ... and though we've still got ways to go, sufficed to say, the 2013 tourney has already been one for the ages.

Yes, after just one week, MMM 2013 has already given us no shortage of shocking upsets, big-time blowouts and rule-breaking so flagrant it forced My Bloody Valentine -- you know, the band that took a twenty year break between albums -- to address the matter on Facebook, which is amazing because we're pretty sure Kevin Shields doesn't even know how to use a computer.

But rather than focus on the negative, as we head towards the end of round one -- polls in all matchups close on Monday at noon ET -- we're going to focus on what has always made MMM so great: the upsets. Simply put, this is the tournament where titans tumble, where David triumphs over Goliath, where underdogs have their day. And this year, things are no different, as a whole host of heavily-favored bands are being put to the test by lower-seeded acts. Can the big boys recover in time, or will the little guys once again rule? That's up to you to decide ... but here's a look at some of the tightest matchups in the tourney.

Let's start at the top of the [article id="1703908"]Midwest region,[/article] where #1 seed the Black Keys find themselves locked in a dogfight with #16 Twenty One Pilots, who came into this year's tournament [article id="1703620"]ready to shock the world[/article] and appear close to doing just that. Will the Keys' run of tournament failure continue in 2013? Right now, it's looking that way ... though they wouldn't be the only high seed to take a tumble in the Midwest: #2 Foo Fighters are days away from yet another early exit (truth be told, they kind of suck in this tournament), this time at the hands of #15 Walk The Moon, who have stretched their lead to more than 2,000 votes. Unless they can close the gap, Grohl & Co. will be watching the second round from home once again.

Of course, it's debatable whether either of those upsets would even qualify as the most shocking in MMM 2013 ... not with what's happening atop the East Region, where #1 Mumford & Sons are going back-and-forth with #16 Japandroids. Right now, the Canadian crushers lead by a razor-thin margin (less than 600 votes in a contest that's seen nearly 70,000 cast). First round exits are, sadly, nothing new for Mumford, who were upset last year by another Canadian band, [article id="1681510"]F---ed Up,[/article] and though we're aware history tends to repeat itself around these parts, we're not ready to pull the plug on Mumford's championship dreams just yet; this is one matchup that's definitely too close to call.

The same can be said about the tilt between two MMM vets, No Doubt and Red Hot Chili Peppers, which is nearing 90,000 total votes and sees ND clinging to a lead of less than 1,000. And don't take your eyes off the Ed Sheeran/Guns N' Roses battle going on [article id="1704131"]down South[/article], where, at the moment, things are locked in a virtual tie (we're not even exaggerating: with 100,000 votes cast, it's Sheeran by two). Could we have our first-ever MMM overtime?

And that's not all: Bruno Mars is getting a rather rude reception in his first tournament, getting trounced by Queens of the Stone Age. Phoenix and Arcade Fire have been trading leads all week (even if the French fellas [article id="1704110"]don't want to win[/article]), and the matchup between Florence and the Machine and Passion Pit seems destined to head down to the wire, with Flo clinging to a slim lead. What all of this change between now and Monday? We'll just have to wait and see!

MTV's Musical March Madness tournament is back! Voting is now open in all first-round matchups and polls close Monday, March 25 at noon ET, at which point we'll move on to the second round of action. All winners are determined by your votes, so if your favorite act made the cut, it'll be up to you to guide them to glory! You can spread the word on Twitter using the hashtag #MMM -- but get ready, it's gonna be a war.