Galvanic Blast

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

Frogmite

Affinity for artifacts (This spell costs {1} less to cast for each artifact you control.)

({B/P} can be paid with either {B} or 2 life.)
Flying
Lifelink (Damage dealt by this creature also causes you to gain that much life.)

Affinity for artifacts (This spell costs {1} less to cast for each artifact you control.)
Draw two cards.

Metalcraft — As long as you control three or more artifacts, Auriok Sunchaser gets +2/+2 and has flying.

This land enters tapped.
When this land enters, you gain 1 life.
{T}: Add {U} or {R}.

Sacrifice an artifact: Atog gets +2/+2 until end of turn.

Affinity for artifacts (This spell costs {1} less to cast for each artifact you control.)
Flying

Metalcraft — {T}: Tap target artifact, creature, or land. Activate only if you control three or more artifacts.