Running pvc conduit into aluminum box

[stryped]

I am planning on mounting lights to the outside of my corregated metal garage. I had planned on using white aluminum wet location boxes that have two mounting ears that screw directly to the metal and running pvc conduit (1/2 inch) throught the metal siding into the back of the box opening. Then running my NM wire into that conduit. I am hoping this gives the best weathertight seal.

Is it allowable to have pvc go into a metal box? Also, I planned on drilling the closest as I can the exact size hole of the conduit in the metal to eliminate a possible leak and using silicone. If I have to use a threaded fitting into the back of the housing, wont that size be impossible to duplicate? Is there a better way to do this?

[resqman]

PVC plumbing pipe is not an approved material for electrical conduit.

There is plastic based electrial conduit. One option is liquidtight non-metallic conduit (LTNM). It is flexible so is easier to run than rigid conduit.

Yes, you can mix metal and non-metal conduit and boxes assuming there is a seperate ground and you are not using the conduit as a ground.