Gliding is a technique available to Meta Knight, Charizard, and Pit. It allows the character to glide in the direction they are facing, and angle up or down, similar to the Cape item in Super Mario World. Once gliding, the character cannot turn around. There is no unlockable character with this ability.
Peach possesses a similar ability in SSBM and SSBB called floating, though it is not identical. Differences include the fact that it has timed usage, can be moved forward or back, and cannot change elevation. The player can activate Peach's ability by holding onto the jump button after jumping.
Gliding after using one's final mid-air jump will put one's character into a helpless state.
All three gliding characters have a unique aerial move when they attack out of gliding. Meta Knight does a single slash downward, Pit does one slash upward, and Charizard spins. All of these attacks do 12% damage, but have varying knockback.
To glide, do a jump, then a midair one. If the player continues holding down the jump button, they will start gliding. Or, at the peak of the jump, rapidly tilt the control stick/pad to also start gliding. Meta Knight can also start gliding by using his Shuttle Loop.
To control the glide, the user must tilt forward or down to angle downwards, and backward or up to angle upwards. The user will go faster if he or she angles downwards/forwards, and slower if he or she angles upwards/backwards. The glide can be ended by attacking or jumping out of it, or by losing all momentum by going upwards (stalling). Jumping out of a glide ends it more quickly than attacking out of it, and can be a better choice if a glide is going off the stage. If the player does not cancel the glide, and move into the stage's surface, the character will crash into it and lay down, as if they had been knocked down.
Since Shuttle Loop always starts a glide, Meta Knight can technically glide twice in one jump.