The Cybermen

Oh crikey! Now then, here's an interesting lot. The Cybermen, originally from the Earth's twin planet of Mondas, and then from Telos, this enemy of the Doctor has been through a few design changes in their time as the world advanced. Originally human like us as their bodies began to die they replaced their limbs with cybernetics and gradually did away with emotions as well, becoming heartless killers who also became age old enemies of the Doctor.
With the new series of Doctor Who well under way the Cybermen made a return in David Tennant's first series, and the revived series's second, on a parallel Earth where they were created to save a dying man live forever. Now personally I despise the new series's take on the Cybermen, to me they look too robotic. In the old series it was obvious that these creatures used to be human, not so now.

The Cybermen

Two versions of an ancient foe of the Doctor’s; our universe and an alternative one

Survival is their main objective

Gradually replaced their flesh with metal

Tended towards covert action, scheming from the shadows

Upgrading is the main objective of the alternative Cybermen

Created to save an insane genius from death

Less emotional then the original version