The Grapple Beam is the name of Samus' extended grab in all four installments of Super Smash Bros. It is a bright blue energy beam that grabs onto opponents and reels them in so Samus can attack them up close, but when it misses, Samus is left vulnerable due to its high ending lag. It is acquired in most Metroid games. When not acquired in a game, it is normally replaced with the Power Grip, allowing Samus to grab ledges. The ledge grab takes on a very important role in the Super Smash Bros. series. The use of the Grapple Beam in Metroid games to attach to certain Grapple points is similar to its special ability in Melee and Brawl of attaching to a ledge from afar (known as a Wall-grapple in Melee and a tether recovery in Brawl).
In Super Smash Bros., the Grapple Beam is Samus' extended grab. This allows her to grab from a far distance, and throw opponents very far with this electrically charged beam. However, it cannot be used in mid-air, which limits Samus' horizontal recovery, and missing with the grab leaves Samus open to punishment for two seconds due to its very high ending lag.
Super Smash Bros. Melee
In Super Smash Bros. Melee, the Grapple Beam can be used in midair, not only to damage opponents, but to perform a Wall-grapple. However, midair use of this attack results in Samus becoming helpless. In the NTSC version of Melee, it is possible to extend the length of Samus' Grapple Beam grab by using the extended grapple advanced technique.
Super Smash Bros. Brawl
In Super Smash Bros. Brawl, the Grapple Beam can still be used to damage opponents in midair, but now the Grapple Beam's Wall-grapple ability was replaced with the ability to perform a long range tether recovery. This gives Samus an advantage since she can recover from afar. On the ground however, the Grapple Beam is slow for a grab, with its traditional high ending lag when it fails to successfully grab. Missing with the Grapple Beam while standing or even while pivoting can result in ending lag lasting well over one second, which is easily punished. However, the dash grab version has much less ending lag than in previous games (though it is still rather high), which may surprise some opponents. The Grapple Beam played a cameo role in the Subspace Emissary, as Samus used it to try to pull a R.O.B. from a Subspace Bomb when Ganondorf ordered the R.O.B. Squad to detonate all of the remaining Subspace Bombs.
Super Smash Bros. 4
The Grapple Beam returns in SSB4, having the same effect as Brawl's Grapple Beam. This move has been buffed overall, it is much faster and has significantly reduced ending lag. As a tether recovery, it has longer range compared to Brawl. Its grab aerial attack now has two hitboxes, with a sweetspot located at the tip of the beam.