This tutorial shows the method I would use to model corrugated metal for siding or roofing for both flexibility and efficiency.

I'd like to point out that I would first try to use a bump map for the corrugated metal if it didn't have to be too close or see the edges.  Here's a link to a tutorial that I wrote a while ago on bump maps that would work.  

http://www.cgarchitect.com/upclose/article30_TB.asp

Download the video tutorial file called CorrugatedMetal.zip and extract the file to your hard drive, and then double-click the HTML file to play the video in your browser.

Good luck and have fun
Ted