[zaric]

Is hydrogen a metal or non-metal?

[Yggdrasil]

It can act as either.  It's one of the cases that doesn't fall into the category of metal or non-metal (or metaloid).

[coinspelunk]

I've never heard of hydrogen being referred to as a metal. Where can it be a metal?

[Telamond]

You can read more about metallic hydrogen here:
http://en.wikipedia.org/wiki/Metallic_hydrogen

[Yggdrasil]

One important property of metals is the propensity to lose electrons and become positively charged.  Hydrogen often will lose electrons to form a positively charged ion (a proton)*.  Of course, hydrogen can also gain an electron (like a nonmetal) to form a hydride ion.

* the true story is a little bit more complicated since hydrogen doesn't really form free protons in water, it forms hydronium ions.

[sm2345]

Due to this both metallic and non-metallic character of Hydrogen, the position of Hydrogen in the preiodic table is debated. Due to this, it is also known as "Rogue Element."