Grey Fox, Metal Gear Cosplay Costume

The main focus of the first two Metal Gear games for the MSX dealt with rivalry between protagonist Solid Snake, a rookie member of FOXHOUND, and antagonist Big Boss, who is initially introduced as the commanding officer of FOXHOUND in the original Metal Gear, but is later revealed to be the leader of the South African fortress of Outer Heaven. In the following game, Metal Gear 2: Solid Snake, Big Boss is revealed to be the leader of the hostile nation of Zanzibar Land in Central Asia, confronting Snake for the second time. Supporting characters during this period include fellow FOXHOUND agent Gray Fox, the Metal Gear designer Dr. Pettrovich Madnar, and Outer Heaven resistance leader Kyle Schneider, all of whom were on Snake's side during the first game but became antagonists in the sequel.
Metal Gear Solid elaborates on the storyline of the early games, by revealing Solid Snake's heritage as a genetic clone of Big Boss, created from a secret government project. There it's introduced a new antagonist in the form of Liquid Snake, Snake's long-lost twin brother and leader of FOXHOUND after Snake's retirement. A third Snake brother also exists in the form of Solidus Snake, who is first introduced as the US President in the end of MGS and serves as the main antagonist of Metal Gear Solid 2: Sons of Liberty. During this time, the cast roster expands to include major recurring characters. Revolver Ocelot, a Russian spy, is introduced as an evil henchman to both Liquid and Solidus but is in truth manipulating them to further the agenda of a third party. Metal Gear Rex designer Hal "Otacon" Emmerich is Solid Snake's sidekick and co-founder of the anti-Metal Gear organization Philanthropy. Colonel Roy Campbell is Snake's former commander in FOXHOUND and former confidant to Big Boss. Raiden, the surprise protagonist of Metal Gear Solid 2, is a soldier trained to replicate Solid Snake's success (not unlike the player(s) themselves, in a way; a major facet of Raiden's character).
Metal Gear Solid 3: Snake Eater, which is chronologically the first game in the series, introduces a younger version of Big Boss during the Cold War, who goes by the codename of Naked Snake. Naked Snake is a former Green Beret. He is supported via radio by the FOX unit, which is led by an ex-British SAS (Special Air Service) agent called Major Zero, Para-Medic (medical support), and Sigint (weapons/equipment support). The game focuses on the rise of Naked Snake from apprentice to legendary soldier, as well as the downfall of his mentor and matriarchal figure, The Boss. The origins of the Metal Gear mecha, the Patriots, the Philosophers, and FOX unit are all explored in MGS3. The game also features a younger version of Ocelot, where his origin as a triple agent for the KGB, GRU and CIA is explored. Metal Gear Solid: Portable Ops, serves as a direct sequel to MGS3 and features some of the same supporting characters, as well as young versions of Roy Campbell and Gray Fox. Metal Gear Solid 4: Guns of the Patriots features the return of several characters that were in the first, second, and even third Metal Gear Solid games.
A motif in the Metal Gear games is the presence of a specialized team of commandos with unique abilities that serve as the bosses in each game, starting with the Outer Heaven forces in the original Metal Gear, followed by the Zanzibar Land forces in Metal Gear 2, Solid Snake's former unit FOXHOUND in Metal Gear Solid, Dead Cell in Metal Gear Solid 2, the Cobra unit in Metal Gear Solid 3, and the "Beauty and the Beast" unit in Metal Gear Solid 4. Metal Gear Solid: Portable Ops parallels Solid Snake's confrontation with FOXHOUND by having his genetic progenitor, Naked Snake, confront his own former unit FOX. A recurring theme amongst the bosses of Metal Gear Solid is that they adopt a name in the form of the "Sons of...". Liquid Snake referred to his army on Shadow Moses as the "Sons of Big Boss", due to everyone possessing genes from Big Boss's remains. Solidus Snake labeled Dead Cell and the Gurlukovich mercenaries under the unifying name "Sons of Liberty", to fit his goal of liberating a city from the Patriots. Though it was not mentioned as much in MGS3, The Pain and Colonel Volgin use the name "Sons of The Boss" in conversations with Big Boss, referring to those who were trained and have fought alongside the Boss. In MGS4, the term "Sons of the Patriots" is coined for the countless mercenaries and PMC soldiers whose minds are controlled through nanomachines.