  We observe the excitation of collective modes in the THz range driven by the
recently discovered N\'{e}el spin-orbit torques (NSOT) in the metallic
antiferromagnet Mn$_{2}$Au. Temperature dependent THz spectroscopy reveals a
strong absorption mode centered near 1 THz, which upon heating from 4 K to 450
K softens and looses intensity. Comparison with the estimated eigenmode
frequencies implies that the observed mode is an in-plane antiferromagnetic
resonance (AFMR) mode. The AFMR absorption strength exceeds those found in
antiferromagnetic insulators, driven by the magnetic field of the THz
radiation, by three orders of magnitude. Based on this and the agreement with
our theory modelling, we infer that the driving mechanism for the observed mode
is the current induced NSOT. This electric manipulation of the Ne\'{e}l order
parameter at high frequencies makes Mn$_{2}$Au a prime candidate for AFM
ultrafast memory applications.
