The Metal Horde is a science fiction novel by John W. Campbell, Jr., first published in 1939. Set in a future where humanity has colonized planets in the solar system, it explores the conflict between humans and an alien mechanical race known as the Sirians. The story addresses themes of advanced machinery, artificial intelligence, and the implications of intelligent machines in warfare, as humanity prepares for an invasion while developing new strategies and weapons to combat the technologically superior Sirians.
