Metroid Prime/Secondary Items

Space Jump Boots
These allow you to increase both the distance and the height you can jump. Jump, then jump again while in the air to do a double jump. This allows you to reach places that were inaccessible with single jumps.

The Space Jump Boots function is similar to the High Jump Boots present in the 2-D Metroid games.

Grapple Beam
Allows Samus to latch on to certain objects and swing on them as if the beam were a rope. Objects which you can grapple onto are marked with a distinctive hook icon; the icon becomes white when the object is in range. While swinging, you can change direction using the analog stick.

Missile Launcher
Though classified as a secondary item in-game, this is actually one of your most useful weapons. A Missile causes a concussive blast on impact that cause more damage than most beam attacks. Missiles home in on the target if you're locked on, ensuring accuracy. Unlike the Arm Cannon though, there is a limit to number of Missiles you can carry. You can increase this limit by collecting Missile Expansions which are scattered around Tallon IV. Each Missile expansion increases Samus' carrying capacity by five, with the Missile Launcher itself having an initial capacity of five.

As a secondary function, missiles are used to clear Missile Door Locks and break obstacles containing Radion and Brinstone. Missiles can also be combined with the Charge Beam to produce Beam Combos (see below).

Charge Beam
The charge beam is an add-on for all of Samus' primary beams; holding down the attack button causes Samus to build up energy which is fired when the button is released, creating a much more powerful attack than would normally result. It also allows access to the various Charge Combos. A drawback is that length of time you need to wait for the charge to build up.

An important secondary function is to draw in pickups (energy and ammo refills) which would be out of reach otherwise.

Beam Combo
The Charge Beam for each beam weapon can be combined with the Missile Launcher to create a Beam Combo. The different Beam Combos are obtained as optional items as you explore Tallon IV.

Expansions
These items increase the capacity of certain pieces of equipment.