The third enemy that Samus encounters. Reos fly up and down in a “V” pattern, waiting for Samus to approach. After they swoop down they will chase her along the ground. They are very aggressive, tenacious beasts that have little concern for their surroundings.
Reos are easy to trick. When they are chasing you along the ground, jump while still moving forward, and the Reo will fly back up towards the ceiling. Use a missile or rapid beam shots to take them out before they catch you.
Reos will almost always leave energy behind after you kill them.