Simple answer - yes. But metal shavings are not the only reason you change your oil regularly. While a permanent or rare-earth magnet can pull the shavings to one side of the flow path, oil degrades in other ways. Also, metal debris in oil is a bad sign of unusual wear on the engine. You usually should have no more than micro particles from wear, even if you don't change your oil often. If your mechanic shows you metal shavings in your oil, he's probably a fraudster and you should get your car checked out by someone else. Or else it means your engine is going to die rally, really soon!