  Ultra hot jupiters (UHJs), giant exoplanets with equilibrium temperatures
above 2000 K, are ideal laboratories for studying metal compositions of
planetary atmospheres. At these temperatures the thermal dissociation of
metal-rich molecules into their constituent elements makes these atmospheres
conducive for elemental characterisation. Several elements, mostly ionized
metals, have been detected in UHJs recently using high resolution transit
spectroscopy. Even though a number of neutral transition metals (e.g., Fe, Ti,
V, Cr) are expected to be strong sources of optical/NUV opacity and, hence,
influence radiative processes in the lower atmospheres of UHJs, only Fe I has
been detected to date. We conduct a systematic search for atomic species in the
UHJ WASP-121 b. Using theoretical models we present a metric to predict the
atomic species likely to be detectable in such planets with high resolution
transmission spectroscopy. We search for the predicted species in observations
of WASP-121 b and report the first detections of neutral transition metals Cr I
and V I in an exoplanet at 3.6 $\sigma$ and 4.5 $\sigma$, respectively. We
confirm previous detections of Fe I and Fe II. Whereas Fe II was detected
previously in the NUV, we detect it in the optical. We infer that the neutral
elements Fe I, V I, and Cr I are present in the lower atmosphere, as predicted
by thermochemical equilibrium, while Fe II is a result of photoionisation in
the upper atmosphere. Our study highlights the rich chemical diversity of UHJs.
