Even a non-ferrous metal can interfere with electromagnetic fields (try dropping a cylindrical neodymium magnet down a copper tube if you don't believe me). The

Even a non-ferrous metal can interfere with electromagnetic fields (try dropping a cylindrical neodymium magnet down a copper tube if you don't believe me). There exist some wireless charging methods that aren't affected by metallic enclosures, but that's not true for all wireless charging in general.