After Moscow was devastated by a nuclear war, the few survivors escaped the radioactive surface and found refuge in the city's extensive subway system. Artyom is a young man who stopped the threat of a mysterious race of creatures known as The Dark Ones, freeing his home station and ultimately humanity itself, and earning the prestigious honour of being a Ranger. Yet the Metro continues to wage war against mutants and political factions such as the Neo-Nazi organization The Reich and the Communistic Reds, and peace is but a dream for the innocent people in the tunnels. Reports soon surface that there is a Dark One that had survived the missile strike aimed at its kind. Through a series of events Artyom meets that Dark One and realizes that things may not be as simple as they seemed.

Based on the Russian novel Metro 2033 by Dmitry Glukhovsky, Metro: Last Light is a post-apocalyptic horror first-person shooter that serves as a new chapter in the Metro saga and is the sequel to Metro 2033. Like its predecessor, the game is a primarily story-driven shooter with heavy stealth elements. Artyom may carry up to three weapons at a time, however bullets are scarce and valuable to the point that higher grade bullets are, in fact, the Metro's currency. When dealing with armed opponents, stealth is encouraged and it is wise to save ammunition for the many mutant creatures encountered in combat. In many situations the player can choose between straightforward shooting and stealth, also having the option for lethal or non-lethal enemy takedowns.

The game takes place in two environments: the Metro itself and the surface. The Metro consists of inhabited stations and tunnels infested by mutants. Each station within the Metro is different, and the player will get to see and visit many of them throughout the game, hostile and otherwise. The surface is a very dangerous place, requiring the protagonist to wear a gas mask to survive, making it crucial to find corpses and containers and scavenge for gas mask filters. Should the mask start to crack and break the player has to find another one, otherwise Artyom will die. The surface is filled with toxic hazards and mutants, some of which can actually pick Artyom up and drop him from great heights.