http://www.youtube.com/watch?v=geTD0gWh8w0

my body is ready guys

plot:
"Earth is burning. Striking from beyond known space, a race of terrifying machines have begun their destruction of the human race. As Commander Shepard, an Alliance Marine, your only hope for saving mankind is to rally the civilizations of the galaxy and launch one final mission to take back the Earth."

The player's choices in the previous games are expected to have a much more significant impact on the plot than the choices in Mass Effect had on Mass Effect 2. As Mass Effect 3 is the end of the planned trilogy, the developers are not constrained by the necessity of allowing the story to diverge, yet also continue into the next chapter. This will result in a story that diverges into wildly different conclusions based on the player's actions in the first two chapters

The story between Mass Effect 2 and Mass Effect 3 is planned to be told through DLC for Mass Effect 2. The Lair of the Shadow Broker downloadable content is the first piece of DLC to begin to expand the story in preparation for Mass Effect 3.

source: ME-wiki