Mounting outside lights on metal building?

[stryped]

I planned to use a motion detector with the two flood lights centered above my garage door. I started cutting thinking I would put a plastic box behind the metal siding inside the garage. However, being centered it is over a raised rib where two panels meet and it looks like I made a mess. It was hard to cut and I just stopped. Any ideas on how to properly mount this light and make it look ok and not leak?

[Mr. Electric]

No!

[Chad Fabry]

The beauty of mounting a light on the exterior of a metal building is you only have to run one wire.