Bulls are a Floating Plant-Type species located on Zebes in Super Metroid within sand traps found in Maridia as well as in parts of the Wrecked Ship. Their appearance is extremely similar to the Puffers, Preeds and variations of the Metroid Prime Trilogy. Their only attack is a quick ram, but they can easily home in on their targets. Their durable armor allows them to survive attacks from most weaponry, but a Super Missile, the Grappling Beam, a few Power Bombs or Plasma Beam shots will kill these creatures.
An untold number of Bulls were captured and brought to the Biologic Space Laboratories research station in Metroid Fusion, where they would later become X Parasite hosts. Bull-X no longer attempt to ram their opponents and instead float around aimlessly. They will expel toxic gas from their orifices whenever they are attacked, as with the Puffers and Preeds. Bull-X also have strange blue coloring which matches their new toxic trait.
Bulls appear in Metroid: Other M in their first official 3D appearance. They appear to have a blue color scheme and expel gas as in Fusion. They appear in the Main Sector and the Biosphere. These Bulls become aggressive as soon as Samus is near them, in which they will charge towards her in an attempt to collide and detonate themselves. Concept art states that they are a plant species that transports seeds by expelling spores in its gas, and that it has been known to easily migrate 100 km by riding on an air current.
Super Metroid refers to them in internal code as a Pipe. 
A Heat Bull is a fiery version of the Bull that appears in Metroid: Other M in the fire area, the Pyrosphere, with a red coloring and the ability to expel fire. Instead of exploding with a poison cloud, it has a much more violent flaming explosion. Its tubes can be frozen over by the Ice Beam, rendering it harmless until it decides to blow itself up. They are as aggressive as their toxic relatives.
"They charge directly at you."
"Bulls may be low level enemies, but they can still be extremely dangerous. They float in the air and slowly waft toward you as they prepare to attack. If they get too close, they'll knock you off your feet. Regular bulls spew poisonous gas.
- Their name may be derived from their similar behavior to a real-life bull (in the ramming aspect). More likely, they are named "bull" as an homage to Bullton, a monster from the "Ultraman" series that they closely resemble design-wise.
- As mentioned before, Bulls seen in Other M behave quite differently from their original variants seen on Zebes. Since Fusion chronologically takes place after Other M, the Bulls' toxic gas seems to not be a result of X Parasites tampering with their DNA (as initially believed), but instead a result of Galactic Federation researchers artificially modifying the creatures to turn them into efficient bioweapons.
- The Bull graphics in Super Metroid seem to have been reused and recolored for Fusion.
- Metroid Fusion: The Official Nintendo Player's Guide refers to Bulls as "parasite-controlled floating spheres" that contain "poisonous gas".
|Tallon IV||Aqua Reaper • Aqua Sac • Chomper Fish • Fish • Jelzap • Tangle Weed • Tallon Crab|
|Aether||Blogg • Bloggling • Alpha Blogg • Fish • Brizgee • Dark Blogg • Grenchler • Hydling • Krocuss • Phlogus|
|Dark Aether||Chykka • Dark Blogg • Dark Grenchler • Dark Phlogus • Dark Shredder • Flying Ing Cache • Venom Weed • Watchdrone|
|Zebes||Botwoon • Bull • Cacatac • Choot • Draygon • Evir • Gadora • Gamet • Oum • Owtch • Powamp • Puyo • Sciser • Skultera • Tatori • Tatori, Jr. • Yapping Maw • Yard • Zoa|
|BOTTLE SHIP||Fish • Skultera|
|BSL||Evir-X • Gadora-X • Owtch-X • Powamp-X • Mermen Pirate • Sciser-X • Serris • Skultera-X • Yard-X|