This article contains spoilers for the Metro series, and Metro: Last Light in particular.
Dystopian fiction is all about the crushing of the human spirit, regardless of whether it occurs in a fully functioning society or at the end of the world. In Metro this dystopia plays out after a man made apocalypse leaves the surface world uninhabitable for humans.
Humanity has survived near extinction level events in the past but only because there was the option of moving to more hospitable places. In the world of Metro the nuclear fallout isn’t a near extinction event. Instead it is a prolonged extinction event slowly killing off humans, and other creatures, because they have nowhere else to go.
Humanity looks up to the light it will never reach.
The three groups go to war because each one truly believes they can lead humanity into a future where it once again spreads across the world. In a way they’re right; a united front to rebuild society below the ruins of Moscow is the only true way for humans to avoid extinction. It’s an obvious conclusion when you’re looking in from the outside but there’s one thing that gets in the way.
The need to survive is a powerful driving force, and the basic human instinct to beware of outsiders resurfaces too. The general population cares more about where their next meal will come from rather than the long term future of the species. These people will join groups that can offer at least some security against the horrors of the Metro, especially those that will pay so your family can buy food.
However, humanity’s extinction is all but guaranteed and a new intelligent race is ready to succeed on the Earth. The Dark Ones appeared after the nuclear war and started building their own society within the ruins of humanity’s fallen empire. Again humanity’s fear of the Other comes to the surface and the Dark Ones are demonised as monsters who will bring about the destruction of humanity.
Of course humanity falls back on its simplest instincts and declares war. In Metro 2033 Artyom is tasked with finding out what the Dark Ones are, and where they are from. Once that is done he is sent to D6 to find a missile to destroy the home of the Dark Ones, which he does. The Dark Ones seem to disappear forever.
Metro: Last Light returns us to the same world. With everyone convinced that the Dark Ones are gone, they can get back to the truly important nature task of wiping each other out. During this war it is discovered a child Dark One managed to survive the annihilation of his home so each faction tries to either kill or capture him.
The face of hope.
Artyom shares a link with The Dark One and becomes his friend and protector against the other humans. Artyom believes The Dark One will be humanity’s saviour. However, more Dark Ones are found within D6 and the little Dark One leads them into the light while humans continue to wage war in the dark. He tells Artyom that the Dark Ones will come back for the humans when the time is ready but by then it will be too late.
In the final battle of D6 the Nazis, Communists and Rangers all fight to control the military base. As this battle rages on the Rangers decide that the only way to stop this madness is by more destruction, setting D6 to blow.
Artyom and the Rangers make the final decision to destroy D6 with themselves still trapped inside. The base is destroyed and the majority of the warring factions are destroyed.
However, not every member of groups would have been caught inside D6. There could still be small pockets in the different stations around the Metro controlled by each group. The war isn’t over, although it has suffered a huge setback. Each side will blame the others for the deaths of their comrades so they’ll still fight. War will consume the Metro and humanity too.
We view the game and see the Metro and irradiated Moscow as a death trap for the humans because of the creatures that live there. Instead the fact is that this a world that has moved on from the human race, with new species taking their place. In the world of Metro humans are relic, much like the ruins of Moscow. In this new world humans must go extinct so the Dark Ones can save it.