"Machina", known as "Machiners" (マシンナーズ Mashinnāzu) in Japan and Korea (and some video games) and "Machine" in the English manga, is an archetype of EARTH and DARK Machine monsters which debuted in the OCG Premium Pack 9. They are featured in the Structure Decks Machina Mayhem and Mechanized Madness. They are used by Kirk Dixon in the Yu-Gi-Oh! R manga, Blister in the Yu-Gi-Oh! 5D's anime and Bolt Tanner in the Yu-Gi-Oh! 5D's manga.
Jerome McHale explained in a post on Pojo that the reason this archetype name was localized to "Machina" from "Machiners" was that the former name "clearly demonstrates that these are Machine monsters, not other Types of monsters that do work on machines."
"Machina Fortress" appear as a character in Yu-Gi-Oh! 5D's World Championship 2011: Over the Nexus and "Commander Covington" appears in Yu-Gi-Oh! 5D's World Championship 2009: Stardust Accelerator.
The archetype involves either getting the three original "Machina" monsters onto your field and using the effect of "Commander Covington" to Special Summon "Machina Force" or the quick Summoning of "Machina Fortress".
The core components of a "Machina" Deck are "Machina Fortress", "Machina Gearframe" and "Machina Megaform" because of their versatility in any Machine oriented Deck. A common loop in all "Machina" Deck variants is that "Gearframe" and "Peacekeeper" search for each other, always ensuring that there is a Machine monster ready for the discard cost of "Fortress".
Using the "Gadgets" is also recommended, since they can search for more Machine monsters to be used to Summon "Machina Fortress".
With nearly constant discard fodder of "Machina Fortress", numerous decent-ATK monsters, and a destruction-saving Union monster, this kind of Deck plays with relentless Beatdown and some field & hand control.
Structure Deck: Mechanized Madness introduce a new mechanics for the deck, based on destroying Machine type monsters you control to summon other "Machina" monsters (with "Machina Air Raider", "Machina Irradiator" or "Machina Overdrive") or to destroy opponent's monsters (with "Machina Citadel").
The deck can generate more resources from the destructions with cards like "Supply Squad", "Machina Defense Perimeter", "Machine Assembly Line", "Crusher Run" and "Machina Citadel" which can be summoned from the Graveyard if a Face-up EARTH Machine is destroyed.
A weakness of this Deck is being banished, as neither "Machina Fortress" nor "Machina Peacekeeper" (unless it is equipped to a monster) can activate their effects when "Dimensional Fissure", "Banisher of the Light", "Banisher of the Radiance" and/or "Macro Cosmos" is in play. "System Down" and "Karma Cut" are also devastating cards for this Deck, therefore a Side Deck containing "Imperial Iron Wall" and cards that destroy/negate Spells and Traps is needed. "Chimeratech Fortress Dragon" is also another card to look out for, as an opponent can remove all your Machine monsters on your side of the field with its own - or even your own - "Cyber Dragon", leaving your field empty for a 2000-4000+ ATK Beatstick.