My Little Physics: Magic is Magnetism??? · 11:34pm Jul 27th, 2021
I was poking about a concept I'd mused on for a long while, that 'cold iron' spoken of as protection and weaponry against all manner of fae creatures was actually meteoric iron, with a high nickel content. I was hoping to find a conceptualization in actual science that I could play with.
AND THEN I FOUND IT!!! Nickel and iron by themselves both respond to magnets. Most of their common alloys are magnetic as well, or at the very least are 'transparent' to magnetic fields, meaning they will not stick to a magnet, but a ferrous object on the other side of a thin layer of the alloy will still be stuck as the magnetic field passes through the alloy.
BUT!! A very strict alloy of 80% nickel-20% iron BLOCKS MAGNETIC FIELDS COMPLETELY!!! 
Soooooo, if we put into our fiction that magic = magnetism or a similar force in another universe, then it makes PERFECT sense that a rare high nickel- low iron meteor would have anti-magic properties, and a medieval knight in need of a magic sword to stand against magical forces could certainly have found this 'falling star' in apparent answer to his prayer for divine aid! And, take into account that such weapons were also attributed other special properties (resistance to rust) that many nickel alloys exhibit, then we have all the 'factual' basis needed to complete this fictional canon! WITH ACTUAL SCIENCE!! 
Also, it works with the 'star metal' from Conan the Barbarian. 
Oh, interesting! Thanks.
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The late Terry Pratchett had elves with some sort of magnetoreception that iron did Bad Things to. Of course, his elves were also full-on Unseelie so doing bad things to them is a Good Thing.