The Magnet Droid is a Terran unit that uses weapons against their opponets.
2500, during the middle of the Brood War, an abandoned science building was detected, a Terran Expedition Force explored the building and they used the magnet tech and it worked great. 2501, magnets were approved as a weapon, during a fight, they have used this tech to stop a goliath from attacking. July 2501, now that the Dominon used this weapon they have destroyed 4 UED command centers. Since the War Of Aiur, they have hid the weapons so the Protoss couldn't steal it.