""Meta Knight (メタナイト, Meta Naito) is an enigmatic character referred to as Kirby's rival, who often fights with him for different reasons, though they often arrive to the same goal. He always wears a silver mask, and under it, he looks almost exactly like Kirby, though with a blue body and white facial features. He wears a navy blue cloak that can transform into a set of wings, and he wields a legendary sword called "Galaxia." He follows a code of honor, and usually lends Kirby a sword before they fight to be fair. Meta Knight is voiced by Atsushi Kisaichi in Japan, Eric Stuart in the English dub of the anime, and Jay Ward in the English version of Super Smash Bros. Brawl. He is a popular character even among non-Kirby fans.
Meta Knight is often a boss and an ally of Kirby in the games. He first appears in Kirby's Adventure, where he fights Kirby to keep him from taking a piece of the Star Rod to keep it out of Nightmare's hands. He also helps to defeat Dark Mind in Kirby & the Amazing Mirror by lending Kirby his sword, giving Kirby the Master ability. He works to keep the chest containing Dark Nebula out of Kirby's hands in Kirby Squeak Squad. He is the main antagonist of the "Revenge of Meta Knight" mode in Kirby Super Star, in which he attempts to take over Dream Land in order to put an end to the inhabitants' lazy lifestyles. He is a playable character in special modes of Kirby: Nightmare in Dream Land and Kirby Super Star Ultra. He is an unlockable character in Kirby: Canvas Curse as well, and he uses a combination of the Wing and Sword abilities in Kirby Air Ride. Meta Knight appears in Super Smash Bros. Melee as a trophy, and he also appears as a playable character in Super Smash Bros. Brawl, where he utilizes his sword Galaxia as his main weapon. His aerial battleship, known as the Halberd, appears in both Kirby Superstar and Super Smash Bros. Brawl. In both games, its inner quarters are filled with enemies and traps arranged to defend against intruders.
Meta Knight is a main character in Kirby: Right Back at Ya!. He is the last surviving member of the Galaxy Soldier Army, made up of "Star Warriors", of which Kirby is one. They are basically warriors who rebelled against Nightmare, the Knight class being the highest rank. It is disputed whether or not he is the same species as Kirby, since Kirby and Meta Knight share similar physical traits, and unmasked Meta Knight looks nearly exactly like kirby. However, the other Star Warriors come from a variety of backgrounds and races. He works for Dedede in order to help Kirby and keep watch over the activities of Nightmare Enterprises. He wields a golden, spiked sword called "Galaxia", and he often trains or defends Kirby to help him defeat Nightmare.""
Source: Wikipedia, "King_dedede", available under the CC-BY-SA License.