molten metal

Why does the hand not burn when immersed in molten metal?
The famous science program MythBusters (Discovery channel) shows how the finger does not burn when immersed in metal (here is lead) melted.
What happens when you swing your hand over a molten metal?
A much-watched video on LiveLeak shows a man in his hand who doesn't cut the molten metal completely without being injured, according to IFL Science.