Queen Metaria is a malignant, amorphous energy being, similar to the depersonalized Japanese god of evil Amatsu-Mikaboshi. She was born as a result of radioactivity in the sun and is the true mastermind behind the Dark Kingdom. Like all arch-villains in the Sailor Moon manga, she is an incarnation of the final arch-villain, Chaos. Her name is sometimes romanized as Metallia, but later editions of the manga included the author's preferred spelling of Metaria. She is called Metalia in the anime.

In the manga, when Prince Endymion and Princess Serenity were to be wed, Metaria took advantage of those on Earth who despised the union. Such a person was Beryl, whose affections for Endymion were preyed on by Metaria. After the war, Metaria was sealed at the North Pole and placed in suspended animation.

In the 20th century, Metaria manages to return a reborn Beryl to her service and orders her to find the Silver Crystal so it may be used to free Metaria. After Endymion's reincarnated form is captured, Metaria enters the young man's body to use him as a suitable host, letting Beryl die in battle. After Sailor Moon is forced to kill Endymion, Metaria is freed to resume her evil. She is eventually destroyed by Sailor Moon.

In the anime Metaria is much the same, with a few exceptions. She eventually becomes powerful enough to resurrect on her own and then took possession of the dying Beryl, transforming into a towering goddess like creature.

In the English dub of the anime, she is referred to only as the Negaforce, a combination of Negative and Force. This dark lord (or lady) is a god/demon-like creature to the peoples of the Negaverse, and though it is the supreme being of its dimension, and thus not beholden to any being from the human dimension, not even Chaos, her/its role is greatly downplayed. Unlike Metaria, she seems never to have been sealed away and she seems to have always been a faceless diabolic force, content to have Beryl do the actual work.