Tetanus. Caused by tetanus bacteria. Usually due to a contaminated wound like broken skin, stepping on a nail, etc. A tetanus infection can result in "lockjaw".

Rust is iron oxide, the compound that forms when iron or steel reacts with oxygen. If you accidentally eat from rusty silverware, the food may acquire a metallic taste, but it won’t warrant a trip to the ER. Just remember to clean the forks and knives before the next use.