Burns:
Lightning Bolt : Plain and simple. One of the best 1-drop that every red deck should have. Bolt the Bird, they say!
Magma Jet : 2 damage for 2 isn't that bad as you can target low-toughness threats or ping your opponent. What is really good for us is the Scry 2 ability, very rare in red. If you prefer, Abrade can be a good alternative with Liquimetal or your own artifacts, but it might affect your deck stability.
Pia's Revolution : This is one of the two cores of the deck. It will either burn your opponent rapidly until they don't have the choice anymore to let you have your Myrs and artifacts back. Great combo with Perilous Myr or Pyrite Spellbomb. The Spellbomb was actually my win-con a few times, since you should have enough mana to spam it mid-game. Another funny synergy is to use Liquimetal Coating on your Field of Ruin or Ghost Quarter, and then sac the land, get it back or do 3 damage. One last combo that might be worth to do sometimes is to use liquimetal on your Mountains and then Shrapnel Blast them, if you really need that 5 damage to unlock Pia's potential and can't lose any other artifacts. But do that at your own risk, you could lose your land instead of getting it back! ;)
Pyrite Spellbomb : Another surprisingly good 1-drop. Set it on first turn and then wait for the good opportunity to use. You can destroy early threats or burn your opponent, Shrapnel it, or draw a card if you need too. Then with Pia's Revolution, things get spicy. You can do 5, 8 or 12 damage in one to two turn if you have both and/or Shrapnels. Pretty neat for a polyvalent 1 mana card. This is one of the win-con of the deck, as it synergies with almost everything and can finish opponents fast ( with the other cards mentionned).
Shrapnel Blast : Our best burn spell. Deals 1/4 of the opponent's life with 2 mana, and we can do more if it's a Perilous Myr or if we have Pia's Revolution in play. Also, you can sac your Mountains with it, ahah... I like to think of them as volcanos at that point. Anyway, more burn is good (for us)!
Perilous Myr : Cheap creature that can get a lot of things done. Block for a turn? Sure. Burn your opponent for 2? Yes! Potentially kill two creatures for one? Could do that. It will make them think before attacking you, especially as they get low on life and you get Pia's Revolution or Myr Retriever in play. Oh, and of course it's an artifact, too! It means that you can Shrapnel it for 7 damage if you really hate your opponent (not that they will like you anyway with that deck), up to 10 with Pia :) Now, where's that popcorn...
Land Destruction:
Field of Ruin & Ghost Quarter : Nothing much to say, I think we all know them well nowaday. They are great if you want to split the colors of your opponent, and in the case of the Field, to remove the mountains from your library. Reusable with Pia's and Liquimetal in play.
Karn, the Great Creator : The other keystone of the deck. Our main source of land destruction with its +1 ability and Liquimetal Coating. You can also animate your artifacts with it, which is great since we have only 8 creatures, and they will die pretty quick. With its -2, you can get your precious Liquimetal in sideboard or any card for the situation. It can also lock a card with its passive ability. A disaster for any affinity faceoff. With Mycosynth Lattice, it's pretty much a win for you.
Liquimetal Coating : I think it's Karn's "new" best friend. Anything you transmute to artifact will help your Karn. You can also use it on your own permanents (mountains) if you want to blast them. It's an easy land desctruction each turn if you have your planeswalker on the battlefield. Great synergy with Pia's Revolution also.
Mana Fix :
Mycosynth Wellspring : That's the perfect card we needed to balance our low land amount. It will help us get our 4 lands needed for Karn, and with the Wellspring it's actually fairly easy. Then you will either use Shrapnel on it, or animate it with Karn for a 2/2 that will get you another mountain. It's also an artifact, so it means that it works with Pia's Revolution.
Simian Spirit Guide : Best mana ramp in red. I don't think I ever used it as a creature, so I don't count it in my creatures total. What is really good is that you don't need to cast it or put in battlefield to get your mana boost. Allows early Wellspring to fix your land needs (with 2 lands you can still play most of your cards), turn 1 Liquimetal or turn 2-3 Karn.
It's important to consider a mulligan if you don't have them or don't have 2 lands to begin with. Drawing a land might be hard without the Wellspring, so don't count too much on land draw!
Graveyard Exploitation :
Myr Retriever Scrap Trawler : Our other creature. Let us get our Mycosynth Wellspring, Perilous Myr or Pyrite Spellbomb back, and any card from the sideboard that was destroyed/killed ( like Ratchet Bomb. Not good offensive creatures, but since it's an artifact too you can do some nice graveyard exploits with Pia's Revolution and you can always Shrapnel it, of course :)