Machine King (series)
"Machine King" is a series of monsters who, for the most part, gain ATK when there are other Machine monsters on the field. The lores of some Machine cards mention serving the "Machine King". However, it is unknown which model of the "Machine King" they serve (most likely "Machine King", since it was generally the only card of that name out at the time of their release, but this could generally mean any of them).
A Machine King Deck focuses on the titular cards and swarming the field with Machine monsters. However, this is not limited to your own monsters, you can also swarm your opponent's field and then use "DNA Surgery" to change them all into Machines.
This deck is essentially a Billy Beatdown Deck, as "Machine King" and its counterparts all focus on increasing its own attack through your own field presence. Commonly used with it is "DNA Surgery", so that your opponent's monsters are also changed to machines.
Machine support cards such as "Limiter Removal" work well in this Deck too. Although using "Limiter Removal" is somewhat reckless, doubling the ATK of all your Machine monsters for one turn could be just what you need to win the Duel. However, the real power of this Deck lies in your ability to swarm the field with monsters, including your opponent's field if you have "DNA Surgery", because more monsters means more ATK for "Machine King".
"Chimeratech Fortress Dragon" can be deadly in this Deck. Because you can use your opponent's Machines as Fusion Materials for that card, when "DNA Surgery" is on the field you can clear your opponent's field for a direct attack.
Advantages and Disadvantages
This Deck is a good counter to Type-specific Decks, such as Plant, and to Swarm Decks, as they will simply fuel the effect of "Machine King". "Uria, Lord of Searing Flames" is also somewhat compatible with this Deck, as there are many Continuous Trap Cards that are crucial to this Deck.
However, this Deck is weak against mass Trap removal, which is quite common. "Perfect Machine King", in particular, is a Level 8 monster, making it somewhat hard to Summon considering it has no uniquely easy way of Summoning. It is also vulnerable to most card-destruction effects, as it's one of the few newer two-Tributes with no innate effect negation and destruction. "Machine King", as well, is particularly weak even with its effect, as it's ATK is lackluster to begin with and its boost is not that substantial.