The Sword Beam is an alternate form of Link's sword in The Legend of Zelda. When all of Link's hearts are filled, Link can attack from a distance using his sword's projectile power. This power would be used in the TV series. However, it would not be used again until The Legend of Zelda: Four Swords Adventures, when the Four Sword would gain this ability upon acquisition of enough Force Gems to repel evil.
It has been confirmed that Link will be able to perform this attack in The Legend of Zelda: Skyward Sword.