Multiplayer is probably the best mode of the game, as the single player mode story is a bit too short for most gamers. Multiplayer can be played on one Xbox via split screen (referred to as local), two or more Xboxes connected via System Link, or via Xbox Live. I can't speak for system link play since I have not tried it, but going online with this game is great.
Multiplayer Game Modes
Grinder
Modes: Local or singleplayer
This mode consist of the player versus a stream of mech attacks. The object is to see how many mechs you can take down before you get taken down. The first round consists of one mech attacking you. The round progresses until you've killed a number of different mechs. Round two consists of two mechs attacking at one time. Each round gets increasingly harder.
Destruction
Modes: Local and Xbox Live
This is your typical deathmatch mode. Pick a mech, then attack others and see how many kills you can get in the time alotted.
Team Destruction
Modes: Local and Xbox Live
Same idea as Destruction, except you are working as a team. Killing a teammate results in a -1 kill penalty.
Last Man Standing
Modes: Local and Xbox Live
This is a variant of Destruction. The goal is to kill all the other mechs before they kill you. The twist is that once you are dead, you respawn as a human and cannot make any more kills. You can only watch the rest of the battle.
Team Last Man Standing
Modes: Local and Xbox Live
Same idea as Last Man Standing, only in a team setting
Not It!
Modes: Local and XBox Live
Think of tag in a mech. One player starts out as "it". The "it" player is identified by the yellow arrow above his or her mech, and the yellow triangle on the radar. Score points by killing "it", and then killing others when you are "it". You may kill other players who aren't "it", but you'll only score a kill, no points. Points are what matters in this game mode.
If you have experience with the system link mode of play, please let me know!