Metala is a fan made keroro gunso OC and is not in the show or the manga. Metala belongs to Kululustardis on devient art (and here) and sgt frog belongs to Mine Yoshizaki.
Privet first class Metala is part of the BLOODSUN or Bununa Platoon. She cant age and is a cyborg. She is 11 years old, but adding the years of being a cyborg, she would be 30.