My house has a colourbond metal roof. For the past few years i've been using strong magnets to attach the lights to the roofline. Wind/rain has been no problem The Magnets out of old computer hard drives are perfect for this. I just wrap them in a layer of gaffer tape so I don't scratch the roof surface or leave a dirty rust mark. The old HDD magnets also have small mounting/alignment hole in them which is also handy for attaching cable ties/etc too. The old SCSI server hard drive tend to have slightly stronger magnets that your usual desktop drive too. Hope this helps someone out!