Wait a minute, did we forget a letter in that title? Nope! You read it right-- some Lulz users are experimenting with metal filament. (That sound you hear is the future knocking at the door).
Using 3mm metal solder from McMaster, forum user BAM was able to extrude metal into basic shapes. He notes that it flows and clogs somewhat like PLA, that it sticks to painter's tape (with more print bed surface experiments forthcoming), and reminds users that-- just as anytime you would be soldering-- ventilation is very important! You can keep up with the ongoing conversation on the forums.
Printing in metal could open a lot of possibilities. What would you print with it?