Gameplay can be either deathmatch or team deathmatch. Once a player dies, they respawn as an unarmed infantryman. Last Man Standing is a free-for-all with no respawning as a mech. The player or team with the most kills wins. In Destruction mode, the player can choose a 'Mech and fight to the death in deathmatch or team deathmatch. This mode can played with one or two players. In Grinder mode (local play only), the player tries to survive as more and more 'Mechs are spawned into the battle. MechAssault had several modes of combat in which players could engage, often based around by-now-common forms of online competitive gaming. Once the player defined all the characteristics of a game, they could invite other players from their friends list or leave slots open for any online player to join the battle. The player could also create and host an online session of MechAssault. For players who wanted to join a specific type of online session of MechAssault hosted by another player, "Optimatch" allowed the player to specify the criteria for the session they want to join. These features included options for finding and creating online matches, such as the common "Quick Match", which enables a player to find an online match quickly regardless of qualifications. "MechAssault" included many of the basic Live services that are now considered standard on any Live-enabled video game. MechAssault was one of the first games on the Xbox to feature the ability to be played on the Xbox Live service. The game follows the player as, commanded by elite officer Major Natalia and assisted by inept techie Lieutenant Foster, they fight the military forces of the cult, assist in the liberation of the planet from Word of Blake rule, and assassinate Commander Strader. It is later discovered by the player that a rogue technology-worshipping cult known as the Word of Blake has invaded and conquered Helios, and is under the rule of an iron-fisted fanatic called Commander Strader. The Dragoons' ship, the Icarus arrives at the planet and is shot down upon entering the atmosphere, causing the ship to crash-land on the surface of Helios.
The player's ship is hired to investigate the cessation of communications from the planet Helios.
The player is a BattleMech pilot (referred to throughout the game as simply "Captain" or, "MechWarrior") in the employment of an elite mercenary organization called Wolf's Dragoons. The plot of the game centers on an inhabited planet called Helios in the dominion of the Inner Sphere, a powerful coalition of feuding factions in control of large areas of space. MechAssault takes place in the BattleTech universe, a science-fiction universe that often revolves around pitched battles between human-piloted walking, heavily armed and armored machines, called BattleMechs.