They have strange names like dysprosium, praseodymium and samarium, yet they are present in everyday objects like earbuds, LCD TV screens and camera lenses. They are a key component of hybrid vehicles, smartphones, wind turbines and catalytic converters. In fact, most 21st century industries rely on them. They are the rare earth metals, a group of 17 chemical elements that were unheard of a few generations ago. Now they have become essential to modern life – but at a price.