Not to the confused with the SV-001 Type-R, a gold colored Metal Slug.
The Golden Slug is a flight-based Slug similar to the Slug Flyer and Slug Copter. Unlike those two, the Golden Slug acts more akin to a bird (which it's obviously shaped after): flapping its wings to maintain flight and making loud squawks.
The Golden Slug has no Vulcan attached to its body. Instead, it shoots a barrage of missiles located between its "feathers". A laser beam is located inside its mouth.
The Golden Slug appears in scenes where the Regular Army is battling against the Martians. Marco is able to ride it in the Rootmars fight. Before he can do that, the player must stop a roulette that contains an SV-001, a Slug Gunner, and the Golden Slug itself.
In Other Games
The Golden Slug, name expanded to the Golden Slug Phoenix, returns in Metal Slug Attack making its first sprite-based appearance. It is the Regular Army's ultimate weapon created to end the long-drawn battle between the factions. Marco, Eri, Tarma, and Fio all pilot the Golden Slug.
The Golden Slug again has access to its missiles. Instead of firing a laser beam, the Golden Slug produces a large energy sphere (called the "Final Giga Buster") and tosses it in an arc creating a massive explosion when it lands.
When the Golden Slug is deployed, an SV-001 Type-R under a Super Metal Slug Attack runs down the field with the strength dependent on the percentage of the opponent's max base HP. Unlocking the Golden Slug's fourth skill amplifies the frontal attack's percentage. Note that this Ultimate Attack occurs when the deck the Golden Slug Phoenix is placed is fully affiliated with Regular Army units.