[header] How to clean a metal roof [title] Wait for dry weather and overcast skies. [step] Avoid cleaning your roof in direct sunlight. Keep in mind that metal and light-colored paint will reflect sunlight and create glare, which may drastically reduce your vision. 
If the layout of your roof requires you to climb onto it, do so when it's dry out to reduce the risk of slipping. [substeps] Of course, once you start washing your roof, it will get wet and pose a risk.