Metroid Database Bestiary

Life-form of raw energy. Periodically releases explosive segments from its body.
Pulse Bombus are energy beings, invulnerable to most known weapons. Electrical energy can harm them, however. They lack any intelligence beyond an instinctive attraction to other charged energy sources. Pulse Bombus produce energy constantly. All excess energy is shed, regardless of who or what may be nearby.

Bombus can be quite aggravating creatures. If they get too close, they will cloud up your visor with electrical static. You can destroy them easily once you get the Wave Beam, but until then, you're best bet is to just roll out of their way.