The Metal-eating Balloon is an object that appears in the Sonic the Hedgehog television series. It is a chemical weapon filled with corrosive chemicals created by Rotor and used by the Freedom Fighters.
The Metal-eating Balloons are ordinary-looking green balloons filled with corrosive chemicals that dissolve metal. They are small enough to be thrown. Upon impact with an object, these balloons will explode and release a green gas. This gas will dissolve any metal it comes into contact with down to nothingness.
One night, Rotor began producing Metal-eating Balloons in his workshop in Knothole Village, which Sonic would test out. When a Doomsday Pod attacked the village however, Rotor and Sonic could only save a few Metal-eating Balloons before a tree got overturned by the Doomsday Pod and collapsed onto Rotor's workshop. Sonic proceeded to use one of the Metal-eating Balloons to destroy the Doomsday Pod. Later, when infiltrating the Doomsday Machine, Sonic used another Metal-eating Balloon to create a breach in the wall and get inside the machine. The last Metal-eating Balloon was used by Sonic to destroy a Doomsday Pod that he and Sally came across when sneaking into the Doomsday Machine for a second time.