While many people, including some TV weathercasters, say that the rubber tires insulate the car, if you think about it for a minute, you will realize that is not the answer. If the lightning bolt can cross then huge distance between the cloud and the car, of course it can cross the extra few inches between the car and the ground. The same is true for rubber soled shoes.

Instead, the electrostatic charge flows across the metal surface of the car and then to the ground, leaving you safe inside. Michael Faraday did quite a bit of research on this back in the 1840's, using a metal ice pail. When charged with an electrostatic charge, the outside of the bucket would have a strong charge, but the inside of the pail was neutrally charged.

With that said, I would not want to be in a fiberglass sports car or one of the new, "rust proof"(plastic paneled) cars during a lightning storm.