Depending on your experience, skill, preparation and risk tolerance, riding a motorcycle in the rain can be anything from frightening to fun. In any case, it is at least more complicated, potentially more hazardous, and afterward, your bike will need a bath.
Some riders avoid rain, but others, especially in areas with more annual rainfall, learn to deal with it. And odds are if you ride long and far enough, sooner or later you'll be confronted with it, willingly or not.
More: Motorcycle Riding In The Rain And Wind