When Kirby first enters its arena, Metal General remains stationary. But when Kirby approaches, Metal General will activate, slowly rise up, and let out a burst of steam, signaling the battle to begin.
Metal General is a short, robotic entity with a dark blue and light blue paint job with yellow eyes. It possesses a shoulder pauldron above its short left arm, and sports boot-like legs, almost similar to Kirby's. Metal General's right arm is a multi-purpose weapon launcher as opposed to its left arm. Metal General's overall appearance resembles a shark and a slightly a samurai due to a dorsal fin-like structure jutting from its back, accompanied by two small rocket engines beside it and a larger one below them.
In Extra Mode, Metal General's overall appearance remains unchanged; the only exception is having a pink and red paint job instead of the previous dark and light blue one.
Metal General will usually start the battle by using hits cyber-katana. This attack consists of slicing everything in front of it, similar to the Multisword Attack. The robotic general can also fire twenty-four small electric darts, the first twelve first going in vertical and horizontal directions, then the other twelve travel in diagonal directions; these cannot be inhaled. Metal General can spin its laser blade in front of it like a propeller and drive quickly across the arena. It can also fire off small missiles (usually three) that can target Kirby; these can be inhaled for the Bomb ability. Occasionally, Metal General will fire one missile, then quickly follow up with its propeller drive attack. It can do this attack three times in a row.
After losing around half of its health, Metal General will start to short circuit and exhaust a jet of steam. It will then launch a huge rocket that it can ride on and ram into Kirby with; it may attempt to do this up to three times. Whether it fails or succeeds, the general will crash land onto the arena still on the rocket, causing the rocket to explode into lingering flames upon contact. The rocket itself can be destroyed before it is even successfully launched into the air or at any point afterwards, and can also be Super Inhaled for the Crash ability before it lands. Its multi-cyber-katana attack remains unchanged, but its propeller drive attack is much faster. Metal General can now shoot five missiles or three missiles followed by its laser blade attacks. Its spark darts attack are faster and can be performed three times instead of two, making a total of thirty-six. Metal General can also Shuttle Loop in midair, electrifying himself and dive bomb towards Kirby. This can cause serious damage if Kirby were to be hit by the attack, but if the general misses, it will be momentarily stunned. The robotic fiend can also launch three explosive mines, all of which can be destroyed with any move. The mines explode shortly after, but the explosions have a small radius. Metal General can summon three Metal Bits that shoot spark shots at Kirby. These can be inhaled for the Beam ability. When Metal General is defeated, it will fall apart, shut down, and then will explode.
Metal General EX will start off the fight with its propeller drive attack. Instead of stopping in front of the opposite wall, it will turn around continuing its propeller drive attack, stopping in front of the other wall. Its multi-cyber-katana attack is much faster now, with the general slightly moving forward with each slash. Metal General EX can now launch a rocket at will, and like its normal mode counterpart, it can be destroyed, but will leave lingering flames if it crash lands. The general can now launch three mines that explode after a few seconds. This time, it can also launch Spark mines, which release an upward jolt of electricity instead of a fiery explosion. The general can also fire five targeting missiles and fire off five saucer drones. Its spark darts are fired more quickly than before. Metal General EX will also attempt to dive bomb into Kirby after Spark Shuttle Looping in the air. Its stun time is significantly shorter than in normal mode when it crashes.
Once again, after losing half its health, the robotic foe will start to short-circuit. Only this time, it will launch two unmanned rockets, which are used to assist the Metal General EX, who is launching its own rocket in the background. The three rockets will then attempt to ram into Kirby from the background. They will explode into lingering flames if they land (provided that the player did not destroy them beforehand), but the player should be wary that they will not cover the whole arena in flames. Metal General EX's propeller drive, spark divebomb, and multi-cyber-katana attack will remain unchanged, but it will shoot eight targeting missiles and summon five Metal Bits instead. It does one quick spark dart attack as opposed to three. It can launch the usual three bomb mines and spark mines. Metal General EX can now summon six saucer drones and command them up to shoot spark shots all at once.
However, after Metal General EX's health bar is depleted and is seemingly defeated, it will escape to the background of the arena, where the true battle begins against the monstrous HR-D3, piloted by the general himself.
- Aside from the final boss, Metal General EX is the only boss with three phases. While it transitions into a fight against HR-D3 when beaten in EX Mode, since HR-D3 is fought as a separate boss in The True Arena it simply shuts down instead.
- Metal General is the only boss that shows how much damage has been dealt to him without the normal health meter in Kirby's Return to Dream Land and the second in the series, the first being Computer Virus in Kirby Super Star and its remake, though the two do this in different fashions.
- Metal General looks similar to Capsule J2. This may suggest a connection, given how its homeworld apparently is responsible for some of the technology seen in Kirby games.
- Metal General's mega rockets can be super inhaled in order to acquire the Crash ability. The rockets can only be inhaled just before they crash land. They turn into a regular sized star if spat out.
- In Kirby: Planet Robobot, there is a mid-boss that is nearly identical to Metal General called Security Force. These mid-bosses were created after President Haltmann received Metal General's blueprints after traveling to Halcandra (or a planet with a strong connection to it).