Musk, who also runs SpaceX and a number of other companies, has been known to make big often exaggerated promises. For example, he once called the Hyperloop, which was never built, the "fifth mode of transport" and famously promised to take Tesla private in a Twitter post, saying he had secured financing that he didn't have.

Elon Musk has denied that the U.S. government is planning on purchasing $400 million worth of Tesla Cybertrucks.

CEO Elon Musk wants to close down tax loopholes as part of his wide-ranging remit at the Department of Government Efficiency, but