- last post: 01.01.0001 12:00 AM PDT
lol i'll help, but it'll be quite long
Basically the story behind MasterChief (a.k.a John or MC) was that he was taken away from his parents at a very young age (very talented mind you) and trained in the army. He has "enhancements" to his body structure and mind coupled with an armour and shield made him and others (don't remember how many, i'm doing this on vacation) the most powerful people in the UNSC (army's name)
Later on in the MC's career the UNSC encounters an alien race called the Covenant who have declared war with humans with the reason of a "holy war". Soon the Covenant wipe out all the outer colonies of humans and attack Reach the UNSC stronghold. MC escapes aboard the ship called the Pillar of Autumn who's mission is to find the Covenant homeworld. The MC's team mates are stuck on the planet holding off the Covenant force. Cole Protocol states that any ship that encounters Covenant must jump to random coordinates to prevent the Covenant from finding Earth. Pillar of Autumn jumps to random coordinates and arrives at the planet Threshold and an ancient artifact known as Halo. The Pillar of Autumn makes a crash landing on Halo and are soon engulfed in something much larger than the war between the human and Covenant. On Halo they discover that it had the same types of enviroments as Earths and was created by the Forerunner to study and contain the Flood. Now the Flood are a virulent species and an AI named 343 Guilty Spark was left in charge of Halo (or so we think). The AI is bent on activating Halo which is supposed to destroy the Flood but instead destroys what they feed upon (eg. humans, Covenant) and clear the galaxy of sentient life. MC is lucky enough to find out the truth and is able to destroy Halo before Guilty Spark can activate it and is lucky enough to escape.
I'm sorry but that's all i can give you, if you want the details or a better understanding of the story I suggest you read the books. The Fall of Reach, The Flood, and First Strike, those are in order for you and you're welcome.