Leatherneck's real name is Wendell A. Metzger, and his rank is that of gunnery sergeant, USMC (E-7). Leatherneck was born in Stromsburg, Nebraska.
Leatherneck's primary military specialty is infantry, and his secondary military specialty is drill sergeant. Before joining the G.I. Joe Team, Leatherneck was a corporal in Gitmo, a tech sergeant in the 1st Recon Bn in Vietnam, a drill sergeant on Parris Island, and a gunny at Camp Lejeune. He earned a reputation for toughness in all of these places, and while he may not come off as likable, he has proven himself trustworthy.
As a drill sergeant, Leatherneck assumes the role of an enemy when training Joes, turning himself into an insurmountable obstacle. He's proof that you don't need to like your fellow soldiers, in order to fight beside them. Leatherneck is ill-tempered, obnoxious, and holds irrational grudges against those who don't fit his definition of "worthy". The only teammate he seems to connect with is Wet Suit, and according to rumor, the two can't stand each other. Their rivalry stems from the tradition of competition between the Navy and the USMC, but their constant bickering conceals a shared respect.
He first appeared in the Sunbow G.I. Joe second season episode "Arise, Serpentor, Arise!: Part I". He was often arguing with fellow Joe Wet-Suit (who was a Navy Seal). He was known for being uncouth, loud and hotheaded. Leatherneck was voiced by the late Chuck McCann.
Leatherneck played a part in the episode "Let's Play Soldier", where he has an encounter with street orphans in an Asian town, at the same time that Doctor Mindbender and the Dreadnoks are harvesting a special sap, which causes anyone who comes in contact with it to act like mindless zombies. Doctor Mindbender tries twice to offer Leatherneck a piece of gum, which contained the sap as one of the ingredients. Once Doctor Mindbender's plot is thwarted, Leatherneck is able to get the local innkeeper to take the street orphans in as fellow workers, much to the objection of the other Joes, who wanted the street orphans to end up in American foster care.
In the episode "The Rotten Egg", it is shown in flashbacks that Leatherneck worked at a military academy, where he had problems with a tough cadet named Buck McCann. One night, Leatherneck caught Buck and two men smuggling weapons, but was knocked out during the conflict. Some years later, Leatherneck returns to the military academy, only to discover that Buck has taken over the academy, and has allied himself with Serpentor. Leatherneck is trapped following a hunt on him, and Buck leads the cadets to attack the Parris Island Military Academy. Leatherneck escapes, and manages to borrow one of the Dreadnoks' motorcycles. Upon claiming an outfit from one of Buck McCann's soldiers, Leatherneck helps the Joes fight the soldiers, which ends with Leatherneck defeating Buck McCann. Buck and his soldiers are then arrested by G.I. Joe.
Leatherneck was featured in a PSA, where he explains to two girls the horrors of not applying suntan lotion when at the beach.
G.I. Joe: The Movie
Leatherneck also appeared briefly in the 1987 animated film, G.I. Joe the Movie.