Thankfully, Metru Nui was rebuilt once the Matoran came back as well as the repossession of the Staff of Artakha.
Voya Nui: a barren wasteland with barely any resources, dangerous animals, and no contact with the outside world. Overrun by a Quirky Miniboss Squad composed of Always Chaotic Evil characters, the Piraka.
While we're at the Piraka, lets mention their home island of Zakaz: like the above, but every inhabitant is an Always Chaotic Evil loon, and their war never stops. Basically a Wretched Hive.
Bara Magna: Also like Voya Nui, but it's a full-blowndesertplanet. However the villains here are far more cunning and skilled than the zany Piraka.
As mentioned in Western Animation, Cybertron, home of the Transformers, is usually a burnt-out husk of its former self due to eons of war. A good number of continuities also have Earth or whatever other Transformer-inhabited worlds caught up in the war turn into one.