Insight Driver said:A common misconception is that the rubber tires on a car insulate the passengers from a lightning strike. The fact of the matter is that the car body, being metal, routes the current over the surface of the car and does not enter it, then jumps to the ground. A metal cage in which current will not go into is called a Faraday cage, named after Michael Faraday, the father of electricity, as he is sometimes known as in history books.
A bicycle clearly is not a cage. Being metal it is like a lightning rod. The tires offer no insulation from a charge that can blow a hole through an inch-thick steel plate. It is possible that the strike would not go through the rider of the bike, however, it is just as likely as the current will fry the bugger to a crisp. In that case, can I have your bike?
Yup. What he said.
It should also be said, though, that being on a metal bike doesn't make you any more likely to be hit, either. Hell, you could wear foil clothes, and your chances of being hit wouldn't change. It's all about the static electric charge in your local environment and how close the potential difference in charges is to the point at which lightning can manifest.
You can also forget that old saw about lightning never striking the same place twice.