Ok, as far as I know from what i've heard, it's theory and can't exist on earth, but...

 

How would something like this work and be implimented? In a sci-fi manga i havn't read yet, it's used for armor, but that's all I know..

I thought I read something about NASA developing metal foam for use as micrometeorite armor on spacecraft, maybe my memory is faulty. If you had bothered to use a search engine first, you would have found a ton of info on metal foam.

I did, smart-ass. If you don't want to answer a question, then don't answer it.

http://en.wikipedia.org/wiki/Metallic_foam

That was the first place I looked, and all it says is "look, i come in three sizes!". But I found a result that starts from the 'beginning', so it's answered now.

All I know of is Aluminium has a foam version, and I am not sure the casting applications for them.

 

It looks pretty cool though.

you can create something that looks like a metal foam by droping molten metal into water.(don't try this at home or without protection) i done this with tin yesterday. although strictly speaking it isn't a metal foam. and the effect only happens maybe 1 out of 10 times.