Mono-Red Aggro may be a classic archetype in Magic, but unless you count Burn, which typically has one or two splash colors, it hasn't been too prevalent in Modern. There have been a few fringe builds of the archetype around, mostly very creature-heavy, taking advantage of Goblin tribal synergies to make up for the power-level sacrifice of limiting your deck to a single color.
Part of being so creature heavy is to take advantage of Reckless Bushwhacker and Goblin Bushwhacker, which are the most powerful cards for decks full of small creatures. Today's version of Mono-Red Aggro still uses the former of that pair, but it pairs it uniquely with Young Pyromancer.
That new pairing may look natural, since one half creates an army of small creatures that you can pump with the other half, but in practice, Young Pyromancer wants to play in a deck with lots of cheap spells and Reckless Bushwhacker wants to play with cheap creatures, which creates significant tension in deckbuilding.
Getting the balance here is important and quite difficult, but by no means impossible. The spell selection in this list makes a lot of sense toward that end with cheap removal to clear away blockers or provide reach, as well as a nice free spell that plays well with creatures in Mutagenic Growth.
The increased spell count also enables Monastery Swiftspear, giving the deck access to another powerful cheap creature that it otherwise wouldn't. You're going to have awkward draws where Swiftspear is simply a 1/2 with haste, but the upside of the card when your draw comes together is too high to ignore.
Bomat Courier is the last puzzling card at first glance, but on closer inspection it does a lot of important things for the deck. First, the card draw it provides gives you a higher total number of resources, which is the easiest way to ensure you have enough fuel for both parts of the "combo." Second, it's a creature that can be cast with the green mana from Burning-Tree Emissary, so its presence allows for some of the explosive draws that are a staple of the Zoo decks in Modern.
Mono-Red Aggro is always going to be underpowered, and attacking with a synergy angle is one way to compensate for that. There's likely more to be done here in refining the list so that the gears are in the right ratio, and the potential exists for an explosive deck in a format that is slowing down right now.
- 4 Bomat Courier
- 4 Burning-Tree Emissary
- 1 Hellrider
- 4 Legion Loyalist
- 4 Monastery Swiftspear
- 4 Reckless Bushwhacker
- 3 Simian Spirit Guide
- 2 Vexing Devil
- 4 Young Pyromancer
- 18 Mountain