Who cares why, just blow everything up.
Red Faction: Guerrilla is a game strictly about blowing the heck out of stuff. It's because of the very straight forward focus that you get all sorts of crazy ways to, well... blow the heck out of stuff. The first thing you do in the game is get your hands on some remote charges and through a tutorial session with your brother, you blow some stuff up. Unfortunately, your brother quickly gets smudged out by some angry soldiers from the Earth Defense Force, who in a very awkward and overdone cut scene, gun down your brother and don't seem to notice you standing right next to him, so they just leave. You then take up a huge hammer in rebellion, and go forth across Mars blowing the heck out of stuff.
That's really RF Guerrilla in a nutshell. The setting and storyline are all just sort of half-done tactics to motivate you into going out and blowing stuff up. Pretty much all attempts at character development just feel kind of weird, and are so few and far between it just seems like they could have left it out altogether. That being said, the focus of the game (the blowing the heck out of stuff, if you haven't gathered that yet) is enough fun that you can just ignore everything else and have a good time.
Throughout the game you'll be equipped with various weapons and find all sorts of vehicles. Weapons include your hammer, various guns, remote and proximity charges, rocket launchers, and eventually a nano rifle that disintegrates structures (and people) without leaving behind any of those pesky debris. You also find vehicles that range from small and fast to big and slow, that are sometimes mounted with various weapons. You'll spend a lot of time in vehicles, because Mars is a big wasteland with a ton of ground to cover between safe houses, and even some missions will require you to use vehicles to complete your objectives. The other, more interesting type of vehicles are the walkers. Basically, these are huge mechs that you turn into tools of utter destruction, and if you find one, you can pretty much rampage around freely through an entire enemy base without it being seriously damaged. They are pretty rare, though, and there is no method for repairing vehicles that get damaged. My favorite piece of equipment, however, is the jetpack that makes its appearance much too late in the game, and if only it had appeared sooner I must say I would have enjoyed the game a whole lot more from the start.
When you take that huge list of tools at your disposal, and the fact that the enormous map is littered with structures waiting to be blown to bits, you find yourself finding more and more creative and efficient (and funny) ways to take them down. Creativity really does pay off here, and it is hugely rewarding when you start taking down whole complexes in just a few strokes, and the enemy didn't even see you coming. That being said, for the majority of the game it is sufficient to just run in with your all powerful hammer and beat down all the enemies, but at some point the reinforcements they call in will just be too much to handle in that manner, and sometimes even the most thought out plans will backfire or not work out as well, and you'll get stuck inside a half collapsed building with 200 enemies waiting outside with machine guns. The late parts of the game can get sort of frustrating.
Overall, RF Guerrilla is not a well rounded package at all, the settings are all too similar to be interesting for long, the audio is nothing to pay attention to, the story is a weak attempt, and the characters are downright uninteresting. But that all really just doesn't matter when your having fun just blowing the heck out of stuff.