temperature - How is heat dissipated from a satellite or any metal in space?

Convection isn't a usable heat dissipating function in space, because there is no convecting medium.

Radiation, however, works extremely well. Any body in space will radiate in a wide range of wavelengths, and will also absorb radiation.

So any part of a space craft or satellite facing the sun will absorb heat (a net gain) and any facing away will radiate heat (a net loss).

Satellite designers minimise the absorption of energy by the use of reflective foil wherever possible, and provide heat radiating fins in order to dissipate excess heat on the dark side of the satellite.