The Lock-on ability is a staple of the combat gameplay of the Metroid Prime series (except Metroid Prime Hunters). Used by Samus Aran and the Federation Force, locking-on allows her or them to maintain a continuous aim at enemies whether she or they are still or moving.
The Lock-on is necessary for Samus to use a Grapple Point. While locked-on, Samus or the Force can strafe around enemies and dash to dodge attacks while maintaining their view of the target. Samus can stay locked-on even if she dives behind a wall (this is not the case with the Federation Force; they immediately lose track of the enemy), but the lock will break if she backs away far enough. When using certain Visors, a meter detailing the amount of distance between Samus and her target, can appear. If Samus is locked-onto an enemy and fires a Homing Missile, charged Wave or Annihilator Beam, or Seeker Missiles, the attack will home in on and hit the target most of the time. Certain enemies are able to move out of the path of incoming fire. The Seeker Missile's unique ability to lock-on to five targets enables Samus to examine the environment for other targets rather than locking onto just one.
While mostly used with the Combat Visor active, Samus can lock onto enemies or obstacles while using other Visors. Sometimes this is necessary as the Combat Visor will not be able to see every enemy or obstruction Samus faces. When using the Thermal Visor, for example, Samus can lock onto specific heat signatures, a crucial tactic she uses to destroy Thardus and the core essence of Metroid Prime, or onto Power Conduits to power them with a Wave Beam shot. The X-Ray Visor exposes enemies normally invisible to the naked eye, most notably Chozo Ghosts, and is important during the battle with the Omega Pirate and, again, Metroid Prime. In Metroid Prime 2: Echoes, the Echo Visor can track enemies and through echolocation. Samus can only disable Echo Key Beam systems when using this Visor, which enables her to lock onto the keys and shoot them. In Metroid Prime 3: Corruption, the X-Ray Visor is used to lock onto weak points in Phazite, such as the armor of Commando Pirates, Metroid Hatchers, Omega Ridley and Berserker Knights. While locked-on to enemies with Phazite armor, the X-Ray Visor will zoom in on these weak points, coloring them red. The weak point can be attacked, and the enemy killed (except Omega Ridley) with a single Nova Beam shot. Finally, the Command Visor enables Samus to lock onto Command Icons, which instruct her Gunship to land, pick up a heavy object or fire missiles. It is not useful for combat without the ship, however.
The Wii versions of the games feature a Lock On/Free Aim option, where Samus can lock-onto an enemy and freely aim at another part of their body. This is useful for hardier enemies that have weakspots which Samus cannot precisely lock onto. Metroid Prime: Federation Force also has this feature by default.
Metroid Prime manualEdit
"Samus has a wealth of weapons and moves at her disposal, and you'll have to practice with all of them if you hope to keep her alive. One of the most important battle tactics is using the L Button to lock onto targets. If you press and hold the L Button without targeting anything, you will be able to strafe side-to-side by tilting the Control Stick.
However, if you press and hold the L Button while targeting an enemy, you will then circle around your lock-on point by tilting the Control Stick. Additionally, you can perform a quick dash move while orbiting a target-simply tap the B Button while locked-on to leap sideways. Once Samus finds the Space Jump Boots, she can perform a double-dash by tapping the B Button twice. Using these moves will be key to surviving battles with the many enemies Samus will face."