Like a third-string quarterback awaiting his moment in the spotlight, magnesium has been sitting patiently on the light-weighting sideline. But, it may finally get its turn to shine in automotive applications, thanks to several recent breakthroughs.

As automakers and suppliers search for new ways to reduce vehicle weight, some engineers are experimenting with natural fibers. Bamboo, cotton, hemp, jute, kenaf, rice and other crops can be used to produce high-strength composite structures for automotive applications.

WARREN, MI—General Motors engineers have developed a technique to join steel to aluminum with resistance spot welding.

DEARBORN, MI—Roofs made of carbon fiber. Plastic windshields. Bumpers fashioned out of aluminum foam.What sounds like a science experiment could be your next car. While hybrids and electrics may grab the headlines, the real frontier in fuel economy is the switch to lighter materials.

DETROIT—In a bid to cut the weight of its cars by up to 340 kilograms by the end of the decade, Ford Motor Co. is testing hoods and other auto body parts made from carbon fiber.