Painted and plastic road markings, tar strips, and metal are especially slippery, as are wet leaves in the road.
This is great advice. When riding on wet roads, try not to roll over anything that isn't asphalt.
Beyond all the advice, I actually enjoy riding in the rain, once I'm out and in it..... unless it's below 40 degrees, then it can get a bit miserable.
Funny, that's when I enjoy riding in the rain the most because I can wear as much as I want and not get too hot or wet. I dislike summer rain the most because anything that will protect against the rain will be too hot, so my only option is to get wet, which I don't like.