I’m fascinated by the interplay of sunlight and clouds, particularly oddly-shaped clouds and optical effects like haloes and sundogs. The trick with photographing them is that you have to take the picture now. You can’t run and get another camera and come back. You can’t wait until you reach your destination even if it’s only 5-10 minutes away.
Lighting conditions will change. A halo might get stronger, or it might vanish entirely. A cloud that looks like a flaming dragon or phoenix right now will be a dull gray in a few minutes. Patterns of rays will fade from view. I’ve missed my chance a lot of times by being stuck on the road, unable to find a suitable place to stop until the moment had passed.
This last shot is a circumhorizon arc formed by ice crystals. It always appears parallel to the horizon, like a flattened out rainbow, and if the crystals cover enough of the sky it will actually form a circle all the way around the sky. I spotted it while walking back to work from lunch and only had my phone with me — and I actually ran the rest of the way to the office so I could get my camera. I was lucky, since these really don’t appear very often.