Mirran Mettle

Target creature gets +2/+2 until end of turn.
Metalcraft — That creature gets +4/+4 until end of turn instead if you control three or more artifacts.

Gearseeker Serpent

This spell costs {1} less to cast for each artifact you control.
{5}{U}: Gearseeker Serpent can't be blocked this turn.

Metalcraft — Ardent Recruit gets +2/+2 as long as you control three or more artifacts.

Tanglepool Bridge enters tapped.
Indestructible
{T}: Add {G} or {U}.

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

Razortide Bridge enters tapped.
Indestructible
{T}: Add {W} or {U}.

Metalcraft — Carapace Forger gets +2/+2 as long as you control three or more artifacts.

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

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

Thornglint Bridge enters tapped.
Indestructible
{T}: Add {G} or {W}.

Spare Supplies enters tapped.
When Spare Supplies enters, draw a card.
{2}, {T}, Sacrifice Spare Supplies: Draw a card.