When one hears the title The Magnetic Monster, several things might spring to mind. Some dickhead back in the day using a magnet to screw up your precious floppy diskettes (since they could screw themselves up just fine on their own, thank you very much). Someone ruining the masterpiece you created on your Wooly Willy toy. That sort of thing. You probably don't think about an artificial isotope, sucking up energy from its surroundings and growing larger and larger, like the freaking "Chicken Heart" of Lights Out! radio fame.
But that's the case with this 1953 sci-fi flick from co-director Curt Siodmak (who we've already had mentioned this year) that stars Richard Carlson (Creature From the Black Lagoon), King Donovan (Invasion of the Body Snatchers (1956)) and Jean Byron (The Patty Duke Show).