Not to mention--it's like licking a flagpole inwinter, you know...tongues and lips can stick. I've seen mine sticktheir lips to cage wires. I'd avoid metal anything in winter!
I use bowls. Deep ones, so they take awhile to freeze. What they do islick a hole on the edge of the dish and keep it open (like aice-fishing hole) until the next day, drinking periodically throughoutthe day.
Their chins and chests get a bit wet after drinking, but they wash quite quickly so it doesn't freeze on.
A handful of clean snow works as a supplement, especially for lazybunnies. If you're worried about enough water, take fresh bowls outagain later in the day.
Horses, I've heard, get some form of porphyria in cold weather becausethey don't drink as much, and I think it works the same for bunnies. Sodon't be alarmed if you see red/brown/orange under the cage.
I just had a scare that way myself!
Rose