There are plenty of monsters that give weakness to all the different types in Monster Legends. So Magnetism shouldn't be just a weakness to the type but it should also increase the accuracy of metal attacks against it. There is even a weakness to metal attribute by itself. So why have another attribute that does the same exact thing but with a different name?
Plus, it makes sense that metal attacks would be attracted to the magnetized monster and so would make it easier for metal attacks to hit them. So I think magnetism should get a boost. It would make it all the more valuable to have monsters with the Magnetism block trait.
Please consider this small but good change to the game.