Rust is the metal (Fe for iron) turning to the oxide (Fe2O3 normally for iron although there are other oxides).

FORBES: Will Handling Your iPhone 5 Damage It? Maybe...

Rust is visible on the metal parts and there are signs of wear and tear.

BBC: Worn and rusting rocket launcher still capable of killing

This is great news for website designers, Internet entrepreneurs, registered nurses, and masseuses in California, but grim tidings for traditional metal bashers in the rust belt manufacturing states like Michigan, Indiana, and Ohio.

FORBES: Welcome to the Michael Jackson Economy

Ohioans have long had a soft spot for heavy metal, which became more popular when the U.S. Rust Belt lost its manufacturing clout in the 1980s, scholars say.

WSJ: Heady Metal: Scholars Celebrate a Rock Genre's Cultural Bang

If the chip or scratch has already begun to rust, lightly sand the area, and apply a thin coat of primer to any bare metal before painting.

FORBES: Zen And The Art Of Keeping Your Car Looking Beautiful