The Boost Guardian has several different attacks. It has the typical abilities expected of a Warrior Ing—slashing, possession, energy beams, and amorphous transformation. In addition, it can also summon Inglets while in puddle form and boost around the room in the form of a spherical ball. In this latter attack, it can destroy any of the four pillars within the arena as well as any Inglet with which it comes into contact.
There are two phases within the battle, the first fighting it as a regular Ing and in its Boost Ball. While in the second phase, the Ing will constantly boost around the room and move about as a puddle. During this time, the Guardian is only vulnerable to Morph Ball Bombs, but immune to any damage. After some point, it will return to phase one.
"Morphology: Boost Guardian. Boost-powered Warrior Ing. Boost Ball ability grants great speed to enemy. Target can only be damaged in solid form. Find a way to keep it solid. This Warrior Ing has absorbed the power of the Boost Ball. It can boost-blast toward its enemies, using its body as a potent weapon. When it is not in solid form, engaging it in Morph Ball mode may provide better attack opportunities."
The Boost Guardian is physically identical to the Jump Guardian, the only other Guardian Ing to be fought in its natural state.
If Samus damages the Boost Guardian with a bomb while it is in its ball form, it will immediately revert to its puddle form.
The Boost Guardian is widely considered to be one of the most difficult bosses in Metroid Prime 2: Echoes. This is due to several factors:
The player will only have a few energy tanks at the time of the battle, even if they've found every tank possible.
The Boost Guardian's Morph Ball form is invulnerable and capable of dealing heavy damage with its Boost Ball (approximately 50 units with the Dark Suit and 100 with Varia in the GC version - this was toned down in the PAL and Wii versions). Although it can be forced out of the form with a Bomb, its speed and power can make this a difficult task.
The lack of Light Crystals or Beacons forces Samus to take constant damage throughout the battle, and health recovery is difficult (the pillars are destroyed erratically, and taking the time to defeat Inglets can leave Samus vulnerable to other attacks).
The Boost Guardian is fought in a small room with the only available cover - the four pillars - being easily destroyed by the boss's Boost Ball and the puddle forms of the Boost Guardian and its summoned Inglets taking up a lot of the floor space.
Bryan Walker, senior director of development at Retro Studios, claimed that he was never able to defeat the Boost Guardian without going into debug mode. 
The Boost Guardian is the first Ing boss that Samus fights without any accessible Safe Zones. Quadraxis was the second and the Emperor Ing was the third (although by that point Samus has the Light Suit, so Safe Zones are not as imperative). Dark Samus' third battle is also fought without any Safe Zones, although she is not related to the Ing.
"Morphology: Boostlet Boost Powered Inglet. Boost Ball ability grants great speed to enemy. Lure it into destroying crystals in area; the energy within will damage the creature. This Inglet has absorbed the power of the Boost Ball. It is capable of energizing its body and boost-blasting it toward its enemies as a weapon. The presence of the Boost Ball has made the Inglet nigh-invulnerable; only pure light energy can damage it now. Expose the creature to pure light to destroy it."