Konami just announced that Metal Gear Online goes live today on Steam. This includes a class system, 16 player online battles and a revised buddy system.
Metal Gear Online is already available on PlayStation 3, PlayStation 4, Xbox One and Xbox 360 while the PC version releases today, 20 January on Steam. There are tons of customization options in Metal Gear Online so go wild.
Metal Gear Online is part of Metal Gear Solid V: The Phantom Pain that is available on PlayStation 4, PlayStation 3, Xbox One, Xbox 360, and PC via Steam.