Mutants aren't the only things you have to worry about in Metro: Last Light. After the nuclear disaster that birthed the post-apocalyptic world as we know it in Metro, humans have shown that we never change. Infighting was inevitable, and splinter groups began popping up left and right, driven by different idealogies. Fascism, Communism, and Capitalism have all spawned their own factions, none of which seem to like you very much.
So who are you with? A police group of sorts known as the "Order of the Rangers." Sounds pretty cool, but you're not leading an easy life, even by Metro standards. Safe havens are few and far between, but you're a Ranger, and you have a job to do.
Combat is more complex than just running and gunning, of course. As the video points, out, the environment can be used to your advantage. With ammo being so scarce, conserving it is usually a good idea. Stealth kills can be pulled off from the safety of darkness, and you can create more places to hide by taking out light sources. Just be wary that the enemy is supposed to be fairly intelligent about how to force you back out into the open.
Character choices are apparently another part of the game, but we don't get to hear any details of that -- just that they exist, and consequences may be an issue.
Ranger Survival Guide Pt. 2 - YouTube
Metro: Last Light will be out on May 14.