Even though Cybertronian life-forms are quite capable of surviving on purely organic worlds, they sometimes resort to eco-structuring to feel more at home. Eco-structuring is the process of converting a planet into an environment hospitable to mechanical lifeforms, particularly Cybertronians. It can be performed rapidly through devices capable of converting organic matter to technological matter, such as the Key to Vector Sigma. It can also be performed manually in a much more gradual process, such as that performed by the Cybertronian Empire in the construction of the Hub.
It is also known as cyberforming. 
Generation 2 (Marvel Comics continuity)
The Cybertronian Empire, believing organic life to be little more than bacteria and viewing mechanical life as the pinnacle, have been eco-structuring worlds for millennia. They believe this to be construction rather than genocide. The indigenous lifeforms are clinically exterminated, and a metal casing for the planet is manually built. This can seemingly be done quite quickly.
Before War Without End!, Grimlock and his Firestormer team had encountered seventeen "little Cybertrons".
Age of Extinction
Probably the best known image of Cyberforming, dozens of Creator Ships arrive at earth during the era of the dinosaurs, and they immediately begin cyberforming with Seeds. The blast and effect of the multiple seeds killed of the dinosaurs and turned their bodies into metallic skeletons. The Creators then activated their collection drills, where they collected all the metal, (except for one good sample of a complete metal skeleton of a t-rex, found later by humans), and then left.
Later, Galvatron obtains a Seed from Lockdown, (it is still unknown how Lockdown obtained a seed) which Galvatron plans to use on Hong Kong, which will wipe out all human life with a radius of a Nuclear Bomb, and will turn the entire city into metal, which Galvtron hopes to use to build his army. His plan fails when Optimus arrives with the Dinobots and kills Lockdown.