Galvanic Blast

Galvanic Blast deals 2 damage to any target.
Metalcraft — Galvanic Blast deals 4 damage instead if you control three or more artifacts.

Sol Ring

Dispatch

Tap target creature.
Metalcraft — If you control three or more artifacts, exile that creature.

Megatron, Destructive Force

Living metal (During your turn, this Vehicle is also a creature.)
Whenever Megatron attacks, you may sacrifice another artifact. When you do, Megatron deals damage equal to the sacrificed artifact's mana value to target creature. If excess damage would be dealt to that creature this way, instead that damage is dealt to that creature's controller and you convert Megatron.

Megatron, Tyrant

More Than Meets the Eye {1}{R}{W}{B} (You may cast this card converted for {1}{R}{W}{B}.)
Your opponents can't cast spells during combat.
At the beginning of each of your postcombat main phases, you may convert Megatron. If you do, add {C} for each 1 life your opponents have lost this turn.

Megatron, Tyrant // Megatron, Destructive Force

Deadly Rollick

If you control a commander, you may cast this spell without paying its mana cost.
Exile target creature.

High Noon

Each player can't cast more than one spell each turn.
{4}{R}, Sacrifice High Noon: It deals 5 damage to any target.