Monster XP are experience points that Monsters use in Monster Life to evolve. In order to earn Monster XP, Monsters must have their Needs met. The quantity of experience depends on the Need Item they are given, as well as any bonuses that are provided by Boosters and the Monster being on a Habitat of the correct Element. Small quantities of Monster XP are also earned in Battle, but not a significant amount.
After a Monster has evolved for the last time, they earn Energy instead of experience when their Needs are met. When the XP bar fills with Energy, an "evolution arrow" appears above their head, only this time the arrow is gold. Tapping on the arrow will cause rings of light to form around the monster. Every hit in the next fight is guaranteed to be a critical hit.
There are many different ways for a monster to earn experience, which are eating, playing, training and cleaning. you can also earn a monster experience by battling but this would take a very long time for it to evolve.
