In previous eras , such as the Iron Age and the Bronze Age , the discovery of new elements brought forth seemingly unending numbers of new inventions . Now the combinations may truly be unending . We are now witnessing a fundamental shift in our resource demands . At no point in human history have we used more elements , in more combinations , and in increasingly refined amounts . Our ingenuity will soon outpace our material supplies . This situation comes at a defining moment when the world is struggling to reduce its reliance on fossil fuels . Fortunately , rare metals are key ingredients in green technologies such as electric cars , wind turbines , and solar panels . They help to convert free natural resources like the sun and wind into the power that fuels our lives . But without increasing today ’ s limited supplies , we have no chance of developing the alternative green technologies we need to slow climate change .