See this answer.As jtobako was saying, MRI machines have some of the most powerful magnets you will ever see. Provided you have no magnetic metal in your body, even they are not going to "purify" you in any way. The main metals that are affected by a magnet generally don't exist in nature in their magnetic form. Usually they are totally nonmagnetic oxides, like rust.If you must experiment with magnets, though, don't even consider buying from people who promise health benefits. Neodymium magnets are expensive enough without someone trying to rip you off. Instead, buy from a company like K&J Magnetics that sells magnets just for tools and coolness value. To comparison shop, be sure you always divide the price by the number of cubic inches (or cm) of magnet you are buying.