Actually metal's pretty bendy when compared to plastic (most anyway...mmv based upon formula).

The metal construction is what prompted me to switch over to macbook pro's back in the day. The plastic dell laptops i used to use couldn't handle the abuse that it took during all of the travel i was doing at the time (cases kept cracking). I switched to a pro and was rewarded later with it surviving a 5 foot fall from a car rental counter. It bent part of the corner, but the screen was still in tact and it continued to work well enough to get me through the trip. I suspect the plastic alternative would have been toast.

Having kids today and seeing how rough they are with their toys, I'm not confident that a plastic laptop would survive them long.

Metal is technically more elastic than an elastic band. With a Young’s modulus of 69 GPa for aluminum versus just 2 GPa for ABS, metal has the "memory" to snap back from significant pressure. Plastic, true to its name, is far more likely to hit its limit and stay permanently deformed. (That’s why metal bars are used to provide “flexibility” to buildings. Concrete provides the strength)