Today my husband was trying to install some new porch lights. He has just gone back to the store for our third set of lights. The first set didn't hang straight (manufacturing issue). The second set just wouldn't fit with our aluminum siding.
Here is what I learned, if you have aluminum siding, beware. The siding might affect which lights you can buy. Depending on how the electrical box is in relation to the edge of the siding, you might not be able to install fixtures with large "bases" (for lack of a better word). The edge of our siding juts out, so it pushes the bottom of the fixture forward. To have the fixture hang straight, you would have to leave a half an inch gap at the top. See how big the base of your current lights are and how they fit. (If the edge of the siding will hit the middle of the fixture, no problem)