So you're the legendary Solid Snake the boss keeps talking about....
As far as I knew, I only learned about the MG1 and 2 thanks to MGS. So that I would at least be aware of Snakes past before I actually played the game. The story takes place in Alaska in a nuclear desposal facilaty which actually contains a new Metal Gear code named Rex.
Fox Hound members which contain Vulcan Raven, Sniper Wolf, Psycho Mantis, Revolver Ocelot, Decoy Octopus, and their leader Liquid Snake, band together along with the Genome Army and take over the facilaty. They contact the president and demand Big Boss's remains to be handed to them in 24 hours or they'll launch a nuclear strike while revealing the secret development of the new Metal Gear.
Solid Snake gets pulled out of retirement from his Alaskin cabin, and told that he has to put a stop to this before the terrorist can launch a nuclear strike. His old cornel Roy Campbell ( who was the former leader of Fox Hound, and currently retired) is the one who informs Snake of this situation. Which Snake is honestly relunctant to do.
His mission is to also save the hostages the DARPA chief and the ArmsTech President. All this has to be done through stealth as always. But the story takes off through many twists and turns and a excellent cast of characters friend and foe. It's definately a game worth playing if you want to know what this series is about.