Earth is a little blue planet at the unfashionable end of the western spiral arm of the galaxy.
It's not a great place to live, being beset by terrorist organisations, rogue paramilitary groups, corrupted AIs, supervillains, extradimensional despots and two separate species of alien shapeshifters. Much of this is due to the presence of Ore-13, a potent fuel source with mystical applications seeded on the planet by an alien during the ice age.
The main life-forms inhabiting the planet are humans. Sucks to be them.
Earth formed 4.5 billion years prior to the present day.
Earth was seeded with Ore-13 by the Decepticon Shockwave with Ore-13 600,000 years ago, thanks to the planet being the resting place of the Enigma of Combination. Seeking to claim the Enigma, Onyx Prime sent the Eukarian starship Axalon to find the relic. They tracked it to Earth 20,000 years ago only for Shockwave to shoot them down.
The Dire Wraiths arrived on Earth early in the 1800s. In the latter half of the century, the Eukarian Autobot and Decepticons were awoken by American railway workers. A few years later, the Elder Gods invaded Earth but the Eukarian Autobots and their human allies managed to beat them back.
Cybertronians started arriving en masse on Earth in 2001, applying infiltration protocol as they engaged in covert warfare over the Ore-13 deposits. In 2005 the Cybertronians abandoned infiltration as the Great War came out of the shadows.
In 2008, the entire planet was subject to a massive invasion by the alien tyrant known as Megatron. Billions died with New York City being virtually destroyed before the Autobots defeated him and his forces. The Autobots remained on Earth for a year before they left to fight Galvatron on Cybertron and cut ties with Earth for two years afterwards.
In 2016, following repeated Decepticon attacks on Earth, Optimus Prime took matters into his own hands by annexing Earth into Cybertron's Council of Worlds. Humanity, however, took this as a threat, and responded by reactivating the disbanded G.I. Joe and creating the Mobile Armored Strike Kommand. At the same time, Baron Karza discovered the existence of Earth and its Ore-13 deposits. He attempted to teleport the mineral into Microspace to save his realm but this had the side-effect of making the Ore-13 unstable, threatening to rip the Earth apart in mere weeks. Once the heroes of Earth stopped Karza, Optimus invited them all to work together.
Soon after, Karza returned to Earth with an army intending to conquer it as a new home for the people of Microspace. His plan was halted by the combined efforts of the Micronauts, Autobots and Time Travelers. In the aftermath, the Time Travelers proposed a treaty of friendship between Earth and Microspace which Optimus Prime agreed to.
In 2017, Earth appointed Marissa Faireborn as its official representative on the Council of Worlds. The induction ceremony however was interrupted when Joe Colton launched a genocidal campaign on Cybertron out of the belief that its people would destroy Earth. Colton's plan was derailed however by Garrison Kreiger who revealed himself to be an ancient alien wizard known as Merklynn and used the Talisman to transform a portion of Cybertron's underground into "New Prysmos". The act drained nearly half of Cybertron's Energon which, ironically, made Cybertron need their alliance with Earth.