Destro (James McCullen Destro XXIV, Laird of Castle Destro) is an international arms dealer. He wears a metal mask that has been passed down from generation to generation; it is a symbol of his heritage. It's also shiny, like, REALLY shiny.
Destro runs a weapons organization called M.A.R.S., and will often sell to either side of a conflict. As such, he is not an official member of Cobra, but he has a thing for the Baroness, and vainly tries to talk the Cobra Commander out of his crazier ideas. What distinguishes him from his Cobra allies is that he actually has a sense of honor (albeit a skewered one), which has occasionally conflicted with Cobra's more ruthless agendas. Not much, mind you.
Occasionally he dresses in leopard-prints for no purpose other than to look awesome.
Marvel Comics continuity
Much, much later, while Megatron was busy closing a deal with Cobra Commander, Destro and the Baroness were busy being snuck by G.I. Joe out of his own castle, ultimately leaving Scarlett (pretending to have defected to Cobra at the time) seriously wounded. Destro tried, awkwardly, to empathize with Snake-Eyes, who had stabbed Scarlett himself to keep up appearances. Shortly thereafter he and Baroness reunited with Zartan.
Dreamwave Transformers/G.I. Joe continuity
Destro and Starscream plotted together to overthrow Cobra Commander using the mighty Bruticus. When Bruticus was unleashed, Destro came close to success, but had it snatched from his hands by the timely arrival of Snake-Eyes.
Destro had Flight Pods.
Devil's Due Transformers vs. G.I. Joe continuity
The financier and distribution manager for Cobra's development of the S.N.A.K.E.S. and their hotwiring of Transformers, Destro was so impressed by Soundwave that he decided he would lead Cobra's attack on the SPS Research Facility. This display of self-assertion even impressed the mighty Megatron, but it irked Cobra Commander. Despite unexpected resistance from the newly formed G.I. Joe team, the mission was a success.
Years later, he attempted to sell some spare S.N.A.K.E.S. to Mr. Calandero, but Eject destroyed all the Cobra machines on his own. This was part of a larger scheme, sponsored by Cobra-La. The S.N.A.K.E.S. were just the bait, and while on the boat, the Autobots were infected with an organic homing beacon that the Pretender Monsters used to track the Autobots back to their base.
Dealing with the serpents made Destro feel somewhat uneasy, but at least he had Mistress Armada to keep him company and make him feel so very good.