Magnet

According to Balan, magnets attracted metal. (TV: The Dominators)

According to a recruitment video featuring Doctor Anthony Sinclair, head science communicator at UNIT, north magnets attracted south magnets, and north magnets repelled other north magnets. If a north magnet was put next to a west magnet, however, a much more violent reaction would occur. According to Anthony, this was the kind of thing they did at UNIT, stating that they "investigate the uninvestigated". (AUDIO: Recruits)

According to a joke book which the Doctor and Yaz became trapped within, magnets found Daleks attractive. (PROSE: Knock! Knock! Who's There?)