From what I know of how metal detectors work, they are relying on the magnetizeable property of metals. Wouldn’t an iron magnet not change intensity or polarity and thus not be detectable? Also, what about realistic situations where the metal detector is passing over the iron magnet. The intensity of the magnet would appear to change to the detector as it passes over, and thus would in essence cause the detectors shielded thingy to oscillate, but it would be less than 1 hertz so I don’t think it would be detectable from that aspect. Anyways thx for ur time.