The Metal Gear Solid franchise can best be described as an in-depth action/thriller in video game form. The level of storytelling in the game is top-notch (albeit convoluted at times), thanks to the masterful direction of Hideo Kojima, the series' founder. What began as a simple stealth action title soon mushroomed into a worldwide phenomenon that incorporated conspiracy theories, over-the-top villains, and massive bipedal war machines into the mix.
It also introduced a ton of key characters that have become mainstays of the franchise throughout the years. Some have spanned multiple decades, while others were only in there for a short while before making a huge impact.
Roy Campbell
Roy Campbell took over operational duties for Big Boss following his apparent demise at the end of the first Metal Gear game. He helped Snake out on his second mission in Zanzibar Land before Snake eventually left FOXHOUND for the quiet Alaskan life. When next-gen special forces led by Liquid Snake took over a nuclear weapons disposal facility on Shadow Moses Island, Campbell reactivated Snake for an insertion mission.
From there, Campbell showed up in name only as an AI construct designed to fool the player in Metal Gear Solid 2, before finally re-emerging as his real self for one final go-round in Metal Gear Solid 4. He's considered a trusted friend of Solid Snake, and a guy who is constantly faced with hard decisions.
Raiden
Players didn't take too well to the character swap in Metal Gear Solid 2, as they had to give up the iconic Solid Snake in favor of another operative named Raiden. It would take some time before they finally warmed up to the character, thanks in large part to appearances in Metal Gear Solid 4 and Metal Gear Rising: Revengeance.
Raiden's presence in the Metal Gear Solid storyline is significant, as he is tied to a multitude of characters spanning the length of the franchise. His cyborg armor and razor-sharp katana blade helped turn him into a badass samurai action hero, which ended up being just what was needed to make him more palatable.
Meryl Silverburgh
Meryl has a special connection to Metal Gear Solid fans, particularly due to her relationship with Solid Snake, which began in the first game. At the time, story-driven games of this magnitude were only dreamt of but never fully realized. Meryl introduced a human dynamic to leverage the story against Snake's tough-as-nails attitude.
The result was a character that made a major splash by telling the story from a second viewpoint. Later, she'd resurface in Metal Gear Solid 4 as a much more confident and experienced soldier, which was a far cry from her rookie days on Shadow Moses Island.
Zero
Major villains have come and gone throughout the length of the Metal Gear Solid franchise, but Zero has been the guy pulling the strings from the shadows the entire time. He was introduced in Metal Gear Solid 3 as the founder of the elite FOX unit and a close friend of Naked Snake.
Later, it was revealed that this seemingly benign good guy was actually the biggest villain of them all, having orchestrated events that led to the climactic showdown in Metal Gear Solid 4. His plan to dominate the world through the use of the Patriot AIs went out with a whimper when Big Boss took him out while he was in a vegetative state.
Otacon
Otacon's family history has deep ties to the Metal Gear mythos. He was responsible for helping to engineer the Metal Gear REX unit before assisting Solid Snake in its destruction on Shadow Moses. From there, Otacon joined the Philanthropy organization and fought alongside his close friend Snake on a variety of missions.
His grandfather had worked on the Manhattan Project while his parents designed the ST-84 (later known as Sahelanthropus), which led to a massive fight and a series of intense tragedies. Otacon felt cursed by his family's dark legacy and vowed to make it right by joining Snake to help de-proliferate the use of Metal Gear weapons around the world.
The Boss
While Big Boss might be viewed as the toughest dog in town, he received all his training from someone far more experienced than himself. That person was The Boss, an American soldier who led the Cobra unit during World War II at the epic Battle of Normandy in 1944. She's a master of CQC (Close Quarters Combat), which would later lead to her death at the hands of her protégé.
The Boss was actively involved in a series of ultra-top secret missions that were so clandestine, all evidence of her involvement was erased. She became a pawn in a mission to retrieve a massive sum of money on behalf of the States while avoiding a major conflict with Russia at the same time. Her impact on Big Boss's life cannot be overstated.
Liquid Snake
As one of two twins in the Les Enfants Terrible project, Liquid Snake crafted a name for himself as a battle-hardened super-soldier and the future leader of FOXHOUND. When the unit went rogue, Liquid Snake led the team to Shadow Moses Island and took over a nuclear weapons disposal facility, then threatened a nuclear strike using Metal Gear REX.
Solid Snake was sent in to confront his "twin," and finally learned the truth about his own DNA. The two battled it out several times before Liquid Snake was taken out by the biological agent known as FOXDIE, which was injected into Solid Snake to act as a carrier in order to wipe out specific targets who knew too much.
Revolver Ocelot
No other character besides Big Boss has as much skin in the game as Revolver Ocelot. Originally a GRU operative under the command of Colonel Volgin, Ocelot bumped into Naked Snake several times in Metal Gear Solid 3, forming a friendly rivalry that would soon turn into something more concrete.
He would go on to befriend and work alongside Venom Snake, who was revealed to be Big Boss' decoy and then later ran defense for Liquid Snake during the Shadow Moses incident. Revolver Ocelot is a triple agent with questionable allegiances on even a clear-sky day, and his willingness to go to any lengths to facilitate deception almost helped him win the world.
Big Boss
Big Boss is a name every Metal Gear fan knows, right back to the early days. He originally commanded the FOXHOUND unit before revealing himself as the true antagonist, at which point he was taken out by Solid Snake — or so it seemed. In reality, this rouse was designed to thwart the plans of Zero, who had far more ambitious schemes for the world.
The two would meet up again when an old Big Boss finally pulled the plug on Zero's oxygen and made peace with Solid Snake. With every loose end tied up, Big Boss died after being exposed to a new and improved strain of the FOXDIE virus, which was being carried in Solid Snake's body.
Solid Snake
Solid Snake has a story or two to tell. He is undoubtedly the most famous of the Metal Gear Solid characters, despite having dropped off in recent years to make way for the character of Naked Snake, aka Big Boss. The series diverted from the future and into the past in an attempt to build a bridge between installments.
In the process, the story bounced back and forth several times to establish a narrative that found Solid Snake stopping plans for world domination. As the hero of countless missions, and the slayer of several Metal Gear war machines, Snake has earned his stripes. He'll continue to go down in video game history as one of the coolest tough guys on the block, with enough training to wipe out a small army.