On the lanthanides row of the periodic table samarium is the first metal that doesn't rust in plain old air. It also happens to be one of the most of the series though that hardly means you can buy cutlery made of the stuff. In fact, about the only thing where samarium is widely used is as flints in cigarette lighters. This exploits one of the traits of the rare earths which is that they create showers of sparks when struck by another metal as small, overheated particles rapidly oxidize.