Vent and Aile use the M.E.G.A. System (Meta-Encapsulated Granule Awareness SYSTEM), or the R.O.C.K. System (Rebirth Of Crystallised Knowledge SYSTEM) in the Japanese version, to activate the Biometals and transform into a form similar to that which the Biometal was based on. Anyone who uses the M.E.G.A. System is called a "Mega Man". Likewise, anyone who uses the R.O.C.K. System is called a "Rockman". Rockmen typically hold out a Biometal in front of them and cry out "R.O.C.K. On!" to activate the Biometal. This process is called Megamerging in the English version, although the characters still say "Rock On" because the game did not get an English vocal dub.
The player initially begins with only Model X, but upon obtaining Model Z, Model X is used to fuse with the other Biometals. This is called Double R.O.C.K. On in the Japanese version, and Double Megamerge in the English version. At this point, Model X can no longer be used alone for the rest of the game until it is unlocked by completing the game with both characters in normal or hard modes only. Biometals of the Four Guardians from the Mega Man Zero series are found throughout the game, and these are the only Biometals that can be upgraded with Energy Crystals. These four Biometals uses the touch screen in various ways. A seventh Biometal is available after completing the game and fulfilling certain requirements.
The Overdrive Invoke System (or O.I.S.) can be activated on the Biometals of the Four Guardians, giving special abilities to the player. Model HX, FX, and LX will give the player elemental attributes to some of their attacks(similar to the elemental chips from the Mega Man Zero series), while Model PX gives the player the ability to dash through enemies without hurting. By charging their weapons, the four Biometals are also able to perform attacks similar to the Four Guardians. For example, Model HX can summon a hurricane and Model PX can throw a large shuriken. However, O.I.S. consumes Weapon Energy.
Players can also revert back to Humanoid form at any time. Although Vent/Aile cannot attack, dash, or wall-climb without a Biometal, they have some abilities that are impossible to do with a Biometal. Vent/Aile is able to crouch and crawl, fitting through tight spaces otherwise impossible. They will float to the surface of water instead of sink, some NPC characters will be too afraid to speak to Vent/Aile when they are using a Biometal, and enemies will not become hostile in certain areas.
Model X[edit]
Model X is known as the "Blue Mega Man." It is the first Biometal obtained, giving Vent/Aile the X-Buster and one ability from the Mega Man X games. The X-Buster can charge up a double shot, similar to the Buster upgrade from Mega Man X2. Model X is lost early in the game upon receiving Model Z, but can be used again after completing the game as Vent and Aile in Normal or Hard mode. This biometal is based on the legendary Mega Man X.
Model Z[edit]
Model Z is known as the "Red Mega Man." It is not used by Vent and Aile, but only by Giro early in the game. Model Z looks very similar to Zero from the Mega Man Zero series, but has a visor in place of a helmet. Model Z has only the Z-Saber for a weapon, and is slightly curved. Vent/Aile later obtains Model Z but combines it with Model X, forming Model ZX. This model is based on the legendary Zero.
Model ZX[edit]
Model ZX is known as the "Ultimate Mega Man." The result of combining Model Z and Model X, it looks similar to Zero from the Mega Man Zero games and has a gameplay experience similar to that series, with both a ZX Buster and ZX Saber available to the player. Attacks for Model ZX include the second fully charged Buster Shot from Model X, the Kuuenzan (spin slash), Retsuzan (three slash combo) and Gahazan (charged ZX Saber attack)
Model HX[edit]
Model HX is the "Mega Man of Wind." It is a form that resembles Sage Harpuia, with many of his abilities. Vent/Aile are able to air dash both vertically and horizontally, hover, and use Harpuia's double saber "Nitouryuu". The touch screen displays the weak spot in Pseudoroids, the location of the Biometal. It also displays the health of enemies. Model HX has the Thunder element. Attacks for Model HX include a homing electric sphere of energy, a tornado that inflicts consecutive damage and a three hit combo which can be performed by pressing Slice, Slash, Slice. The third strike unleashes a wave of energy
Model FX[edit]
Model FX is the "Mega Man of Fire." It is a form with Fighting Fefnir's abilities. Vent/Aile uses two "Knuckle Busters" (Nichou), busters that resemble Fefnir's buster cannons, Sodom and Gommorah. Similar to Fefnir, Vent/Aile is able to shoot directly up. They also have the ability to create shockwaves on the ground, similar to Fefnir's Earthquake attack. The touch screen displays FX's special ability, "Buster Edit." The player can draw on the touch screen a path for which the buster shots from either buster will follow. Upgrading FX will allow the player to draw longer paths. Model FX has the Fire element.
Model LX[edit]
Model LX is the "Mega Man of Ice." It has the form of Fairy Leviathan. Using a Halberd for a weapon, Model LX lets Vent/Aile swim and dash freely in water. The touch-screen displays a map of the surrounding area. A Cyber-Elf icon appears on the map to highlight any nearby items. Model LX has the Ice element. Charged attacks for Model LX include an ice platform that can be used to cover vast distances and a homing ice dragon attack (Horyuu). While in water during Swim, the player can spin the Halberd indefinitely by pressing alternatively between the main and sub weapon buttons
Model PX[edit]
Model PX is the "Mega Man of Shadow." A form with Phantom's abilities, it uses kunai for weapons. PX can also latch onto ceilings and other objects such as poles and platforms. A radar is displayed on the touch screen, highlighting enemies and showing passageways that may be hidden. Also, while in overdrive mode, dashing will make you momentarily invulnerably to enemy attacks. Model PX is also able to see farther in the dark. Model PX has no elemental attributes. Charged attacks include a large shuriken and a barrier that absorbs weak shots indefinitely.
Model OX[edit]
Model OX is a special Biometal that is available after completing certain tasks. Vent/Aile will look like a duplicate of Omega Zero, the final boss of Mega Man Zero 3. Model OX has many abilities similar to Omega Zero, executed with certain button commands while in Overdrive and it has infinite Weapon Energy. Many of Model OX's special attacks are based on the various attacks Zero used in the Mega Man X series. Model OX is only unlockable in Normal or Hard mode. Model OX has the same charged attacks as ZX, but changes while in Overdrive.
Attacks while in Overdrive with OX Saber include Arc Blade (an ice elemental Kuuenzan that fires small waves of energy in all directions), Ryuuenjin (a rising fire uppercut) and Shinkuujin (a Thunder-elemental wave of energy) Attacks while in Overdrive include Earth Crush (spits up four boulders from where the ground was punched), Messenko (fires 9 bolts of energy from where the ground was punched in a fan-spread fashion) and Rekkoha (summons piercing rays of energy from the sky and ground to fill the screen). Instant Charged Shots also available. You can also charge your buster shot to a higher level, this charged shot stores one extra shot after release in the same fashion to that of Model X's Buster Shot.
Model W[edit]
Model W (Model V in the Japanese version) is the original Biometal, formed from the pieces of the core of the Ragnarok Space Station that Dr. Weil (Dr. Vile in the Japanese version) fused with, which was destroyed at the end of Mega Man Zero 4; the Biometal is supposedly a piece of Ragnarok that contains Weil's soul. The original Guardian commander studied these pieces and developed the other 6 Biometals to stop Model W. A small fragment was later found by Serpent 10 years prior to the game, triggering the Maverick outbreaks. It is used only by Serpent at end of the game.