To provide a workpiece impact driving metal staple for fixing an object to a metal frame.

A metal staple is characterized in a shank part 3 comprising a peak part 10 and an opposite end which is aligned substantially parallel to a head part 4 and integrally connected thereto. The head part 4 is provided with at least one recessed part 12 for reinforcing the capability of fixing a lining such as a wire mesh or the like to a metal frame 14 opposite to the shank part 3, and the width 'W' and a thickness 'T' of a shank member in an area between the peak part 10 and the head 4 shown by letters 'Y'-'X' are set in such a manner that at least the peak part 10 can pass through a metal frame wall with a regulated thickness G.