After creating or importing a character, you will be thrust right into the war against the Reapers. The first mission of the Mass Effect 3 campaign will be a tutorial of sorts. Already on Earth, Shepard will be tasked with defending Canada from the Reapers’ armies. As this is a tutorial, the combat will not be much of a challenge and your weapons and abilities will be somewhat limited. You will only be able to use the default Predator pistol, and your powers will be similarly limited to whichever abilities default to your class.
You will be fighting alongside Anderson. Follow him to the wall, where a group of husks will begin climbing over. After you kill these husks, look below you to find another group. Use your powers or melee attacks whenever possible, as your ammo will be fairly limited in this early level. When you have finished with the attackers, head into the burning room ahead and collect the medi-gel inside. When you open the door, another husk will burst into the room. Kill it and head out.
This next area will introduce you to a new enemy type. The cannibal enemy type wields a rifle and grenades, and as their name implies they can actually consume their fallen brethren to recover health. Despite these advantages, they are somewhat weak when taken alone, as they have no armor and their health is low. Take cover, wait for a break in their fire, and pop up to return the favor.
Follow Anderson to the crash site. Here you can pick up an Avenger rifle. Grab it before examining the radio. At this point, waves upon waves of cannibals will begin to swarm the area. These enemies can only become more formidable as you kill them, since they can eat each others corpses to regain their health. It is a formidable ambush. Take cover and fire away with the Avenger. As long as you stay safely behind cover, this section shouldn’t be too difficult. Venture out on your own, however, and you can easily die. Once you have emptied the Avenger, switch to the Predator pistol and keep firing. A scripted segment will occur when you have depleted your ammo reserves. Just as it seems that the cannibals will overwhelm your position, Joker will arrive with the Normandy to whisk you off to your next mission.