As with most bosses in Raider Zero, the Cargo Mech has little to do with the plot and only serves as a barrier to the Sewage Treatment Facility.
The battle's setting is on two platforms, one above the other, and the rest is flat ground. When Arkus walks forward to the centre of the room, the Cargo Mech activates and attacks. It has two "hands", one with a powerful laser, and one that fires projectiles in eight directions. Simultaneously, the head uses a cannon that locks on to Arkus, and missiles that do the same. After the head, hands, and legs are destroyed, the torso fires homing energy balls, and the missiles still launch at the player. At that point, the green core of the exposed torso becomes its weak point. Destroying it will defeat the Cargo Mech.