Maltus was home to an ancient, nearly forgotten civilization that gave birth to the Maltusians; a race which eventually evolved into the Guardians of the Universe, Controllers, and the Zamarons over 10 billion years ago in the DC Universe. Maltus is known to be an extremely overpopulated planet which serves home to a poverty-stricken humanoid race with the inherent potential to evolve into Guardians of the Universe.
While advanced in technology, Maltus suffers from severe problems due to their overpopulation, as detailed in Green Lantern.
It was revealed in Secret Origins (via Heru, a Guardian, and Nadia, a Zamaron) that life evolved on Maltus very similarly to Earth. Maltus had its era of dinosaur-like creatures previous to the humanoid race. It was also revealed that a new organism sprung up on Maltus, called "symbiotes." The symbiotes merged with the humanoid race and gave them their advanced intellect, along with the building blocks to becoming immortal. It was revealed that the symbiotes were the source of all the powers granted to the race of humanoids that eventually evolved into the Guardians of the Universe.
The Guardians, Controllers and the Zamarons eventually left Maltus to further their own agendas. The Guardians set up on the planet Oa, the Zamarons went to a new planet and named it Zamaron, and the name of the Controller homeworld is unknown.
Maltus resurfaced in Trinity which introduced the Triarch, a trio of Maltusian gods. It was during this mini-series that the Maltusians revealed an ancient prophecy about Green Lantern John Stewart.
Recently, Maltus was revealed to be the home planet for Vril Dox's robotic L.E.G.I.O.N. force. It was also the first planet to fall to Starro the Conquerer when Starro's vanguard forcibly took control of Dox's robotic peacekeepers. The planet's population has since been turned into Starro's mind-slaves, with a few pockets of resistance. Maltus is currently serving as the home base for Starro's latest invasion.
The name Maltus is a nod to the demographer and political economist Thomas Malthus, who predicted for Earth overpopulation problems similar to those the fictional planet had to face.