If you have a metal roof, you may want to clean it annually. That keeps your roof looking visually appealing. In addition, regular cleaning also makes it easier to stay up to date on maintenance, as you can take note of issues and attend to them right away. If you don't clean your roof, you may not notice some of these issues, and they may get worse. To be effective, however, there are a few cleaning and safety mistakes you may want to avoid.