Solid Snake is the main protagonist in Metal Gear Solid and for a short time was the protagonist in Metal Gear Solid 2. He has an IQ of 180, speaks 6 languages fluently, is an expert in scuba diving, rock climbing, parachuting and has an in-depth knowledge and expert skill with almost all types of munitions.

He is a clone, one of three survivors of the Les Enfants Teribles project, which had 8 clones to start with. He is genetically identical to Liquid Snake and Solidus Snake, the other survivors of the project. They were cloned after Big Boss, AKA Naked Snake in 1972.

Raiden is the protagonist of the Plant Chapter in Metal Gear Solid 2. He was a child soldier in Liberia, where Solidus Snake adopted him after killing his real parents. he was nicknamed 'The White Devil' and 'Jack the Ripper' for the amazing kill record he had. he has a current love interest with his coworker, Rosemary. He receives help from Pliskin (Solid Snake) during the plant chapter, and proceeds to defeat Solidus in a sword fight on the Federal Hall Building in manhattan after Arsenal Gear crashed into it.

Liquid Snake is the final boss in Metal Gear Solid 1, which consists of 3 battles; the fight with Metal Gear REX, the fight on REX, and the chase sequence in the jeep. He leads the Special Forces unit FOXHOUND, which he convinced to become terrorists along with the Genome army to get the remains of Big Boss and destabilize the world by launching a nuke. He is killed by FOXDIE, a genetic virus that targets people based on their genetic code. Ocelot replaces his right arm that was cut off with Liquid's arm, and if Solid Snake is near Ocelot then Liquid can usurp control of his body from him, through the arm, as seen in the Tanker and Plant Chapters in Metal Gear Solid 2.

Solidus Snake is the final boss in Metal Gear Solid 2, and is the last survivor of the Les Enfants Teribles project. He utilises armor which is impenetrable to gunfire, dual swords (the Democracy and Republic blades) and a P90/ His suit allows Solidus super human strength, and has two prehensile tentacles which can shoot missiles. He is the foster father of Raiden, and leader of The Sons of Liberty, a terrorist group bent on destroying the Patriots (an Illuminati-esque group) control over America, to turn it into a true democracy. He attempts to kill Raiden to get the nanomachines in his body, which has the locations of the 12 highest ranking members in the patriots, but later on it is discovered that those members have been dead for 130 years.

The GRU Soldier operates under Russian government. They are the main enemies in Metal Gear Solid 3. Their arms vary from AK's and grenades to shields to floating platforms armed with a machinegun. These guards are the first to be able to hear Snake walking (besides on metal) and are able to be interrogated.

The Ocelot Soldiers are the elite of the Spetsnaz, and are commanded by Ocelot. they are crackshots, and use a variety of weapons with great effiency, from the Dragunov SVD and M63 Stoner Machine Gun to the Vc61 Scorpion Sub Machine Gun and AK 74's. They carry rare and deluxe items in Metal Gear Solid 3 such as batteries, Instant Noodles, and medicine.

Genome Soldiers are regular soldiers who have been genetically modified with Soldier genes; 52 genes which make the perfect soldier. These are the Main enemies encountered by Solid Snake. Being genetically identical, they feel they are brothers, and later cooperate with Liquid Snake and the newly formed FOXHOUND unit which went renegade, since they need the genes of Big Boss to finish their own genes. They usually only carry FA-MAS and wear snow-suits and gas-masks.

The Leone unit is commanded by Leone, a man form America who served in Vietnam, and was acused of being a traitor. It is unknown as to whether he actually is one. His unit consists of 100 men who had their homes stolen, destroyed or otherwise ruined by the US. They wield shields, AK's and grenades, and also have hijacked UAVs and Patrolbots. They are the main enemy in Metal Gear Ac!d, but the surviving members get treated with ACUA (Acting Cells Under Alice), which makes them slaves to Number 13 (Alice). It is believed that Leone also takes ACUA, as an explanation to him hallucinating Pansies.

The SL Security Force (SaintLogic) is headed by Vince. He utilises an RPG and his super human strength to defeat his foes. the security force he heads is diversified, featuring the average grunt to Tengu soldiers to commanders. The SL Security force was Snake and Venus' main enemies in Metal Gear Ac!d 2.

The ACUA soldier is actually just anyone who has been given a dose of the ACUA drug (Acting Cells Under Alice). ACUA allows number 13 (Alice) to control whoever has taken the drug. They are turned into ruthless, skilled killers and lose all memory of family, friends and loyalty. Most of the people who were treated with ACUA were formerly Leone soldiers.

The Gurlokovich soldier serves under Colonel Gurlokovich, a man dreaming to restore the motherland. He has ties to Revolver Ocelot, and has a daughter named Olga. He is betrayed by Ocelot in the Tanker Chapter of Metal Gear Solid 2, and dies of drowning (after being shot by Ocelot, under order of the patriots). The Gurlokovich soldiers have a variety of equipment, from AK's and grenades to shotguns and shields, and the Tengu version, which wields a High Frequency Sword.

Fat Man is an obese man who at the age of 10 built an atomic bomb by using a handbook from the internet. He planted bombs on the Big Shell in Metal Gear Solid 2, and was the first boss fight in the plant chapter. He uses roller skates to move quickly, and wears an extremely heavy protective suit which is nearly impenetrable to gunfire.

He first joined NAVSCOLEO, then was kicked out and was taken in by NEST, but left and joined with Dead-Cell, the terrorist group in the Plant Chapter of Metal Gear Solid 2. He was operating under the orders of the Patriots, an illumnati-esque group to test Raiden on his progress.

The End is a sniper that is over 100 years old, and is called "The father of modern sniping". He is a member of the Cobra Unit, and taught The Boss everything she knows about sniping. His rifle is a modified Mosin Nagant, which is an M1981/30 which shoots tranquilizer darts. He is also a master of camoflauge, and can perfectly blend into a forest environment, as well as reduce his body heat to blend in. His body has also become somewhat like a plant, and he is capable of photosynthesis, allowing him to live without food for extended periods of time. He sleeps to conserve his energy for his final hunt.