You play as Marcus Fenix who is in prison because of a court Marshall but that's all you find out. Marcus is one of the toughest soldiers I've ever played, he saw every thing on E day (Emergence Day) when the Locust come out to play. You then have four other soldiers in Delta squad who are: Dominic Santiago your best friend who has lost everything he very cared about he has no fear of dying now, Baird who'll always say the funniest of thing in the worst situation you could be thrown in, Augustus Coal or known by his thrashball (version of American football) nickname "Coal train" he bought his strength to the CoG (Coalition of Gears) and the last soldier is called Anthony Carmine who's the least experienced soldier in Delta squad but makes up for it in enthusiasm. They will all follow you though hell and back.
You start off in a dark prison with your best friend Dom helping you break out. He gives you the option to train your aim or you can just jump in there: doing the training just gives you some tips, choosing to jump in there, you get dropped into a fight with 3 enemies called the Locust, here you can see how awesome the gun you have called the Lancer but it's not your standard machine gun, oh no it's more it has a chainsaw which by pressing the B button you can rev it up, run up to the enemy, make short work of them and watch the blood squirt on your screen and watch the enemy disappear into little bits.
You don't really know anything about whats going on at the start but you soon find out how screwed the world is, you are fighting an enemy that just wont give up. But thankfully you have the best fire power that can make lite work of the toughest Locust.
If I had to sum up the campaign in one word it would have to be, Amazing it's one of the best games I ever played on Console, it's about 8 hours long on normal difficulty, on insane than it could take how ever long it takes you to pull of prefect head shots. If you rage easy then insane isn't for you but to get there you need to finish it of on easy/normal/hard first, even hard is a tough challenge but when you finish it, it's one of the best feelings you can get from finishing a game.
There's really only one way to talk about the online, if you don't use the shotgun it's going to be tough and your aim has to be 100% on the small/mid sized maps on the bigger maps then you could do well with any type of aim with any gun.
If you haven't played it you're missing out on the Xbox 360 hit of 2006, the graphics were good when it came out but if you're a graphics kind of gamer it might not be your game.