Shielding is a defensive technique first introduced in Melty Blood. A form of this mechanic also exists in the Super Smash Bros series, as well as the BlazBlue series, though under the name of Barrier.
Shielding in Melty Blood
Executing by pressing the D button (not to be confused with ), the character will put up a small energy shield that will nullify one hit of the opponent's attack. Like blocking, some attacks can only be shielded high or low. Holding the button will continue to hold the shield up at the expense of the player's power bar. Shielding an attack just before it hits is known as EX-Shielding. Whether an attack is shielded or EX-shielded, the shielding player will gain 5% of their meter (equivalent to about 50 power in M.U.G.E.N), while the attacking player will gain none and will finish their attack animation. Performing an EX-Shield during Blood Heat mode will automatically activate a specialized counterattack super known as a Last Arc.
Shielding in Super Smash Bros.
In the Super Smash Bros series, like in Melty Blood, shielding puts up a shield that will nullify the opponent's attacks. Unlike Melty Blood, shields in Smash Bros can absorb more than one hit as long as the button is held down, but will decrease the shield's stamina the longer the shield is held and as the shield takes damage. Shield stamina will regenerate over time. Whenever the shield's stamina is reduced to 0, the shield will shatter, causing the user to flip and become stunned for a few seconds, rendering them vulnerable to attack. The shield can also be easily broken by items such as a Fan, Mr. Saturn, and Hammer. The shield cannot stop grabs, though. In Super Smash Bros. Melee, you could create a larger shield by holding Z that shrinks slower than a normal shield, but has larger block stun upon being hit.
Shielding (Barrier) in BlazBlue
In BlazBlue, if you press LB on Xbox, and R1 on PS3, your character will make a barrier in front of them. when this occurs, if the opponent attacks, the barrier will nulify that one hit only once for the rest of the match. Once it's hit, it lowers your character's defense stat, making it very risky. There is a bar, marked Barrier, that is underneath the character's lifebar, that graphs how long the barrier can stay up. Like in Super Smash Bros, it cannot stop grabs.