Whether you drive a Chevy Spark or a Ferrari F12, take a walk around it and you'll find a remarkable amount of plastic on the body: Mirror housings, trim panels, wheel well arch trims and the bumper covers that define the face of the car are all likely plastic. 

This irks some people, those who still think a good car is heavy on the sheet metal, but carmakers haven't swung to plastic entirely out of a desire to cheap out. When it comes to exterior parts in particular, there are five main reasons you'll find a lot of plastic there now and more in the future.

• Cheapness: Yes, plastic is generally cheaper than automotive-grade aluminum and steel. But we're just getting started...
  
• Formability: Before World War II, "plastic" was typically an adjective, not the noun it is today. You can mold plastic parts into shapes and even textures you just can't with metal, at least not without a very expensive process.
  
• Flexibility: A plastic bumper bounces right back from low-speed parking lot bumps in a way old chrome bumpers never did. Insurance companies love that.
  
• Lightness: This is a big deal in a business where automakers try to save every ounce of fuel to hit aggressive MPG and emissions goals. 
  
• Rust resistance: Most metal on a car today is very rust-resistant, but plastic is rust-proof. This is particularly handy on those bumper and fender parts where salty water tends to collect.
  

Beyond all these rational reasons cars have a lot of plastic, there are emotional ones: Black plastic trims tend to make a car look sportier, more rugged and more youthful. Find me a carmaker that doesn't want to push all of those buttons.