Wear resistance is critical in bearings for all modes of transportation and in machine tools. Fatigue resistance the ability to resist breaking after repeated deformation such as bending enables the use of metals in springs, levers and gears. Temperature resistance makes metals suitable for jet engines and filaments in light-bulbs. Metals are uniformly lustrous and, except for copper and gold, are silvery or greyish. This is because all metals absorb light at all frequencies and immediately radiate it.
Metals impart the reflective surface to mirrors.
The lustre of metals gives them the attractive appearance that is so important in jewellery and coins. Ferromagnetism is exhibited by iron and several other metals. In addition, other metals and alloys can be magnetized in an electrical field to exhibit paramagnetism. Magnetic properties are employed in electric motors, generators, and speaker systems for audio equipment. These phenomena are exploited in television screens using rare earth oxides and in a variety of electronic devices and instruments.