  The circumgalactic medium (CGM) of galaxies serves as a record of the
influences of outflows and accretion that drive the evolution of galaxies.
Feedback from star formation drives outflows that carry mass and metals away
from galaxies to the CGM, while infall from the intergalactic medium (IGM) is
thought to bring in fresh gas to fuel star formation. Such exchanges of matter
between IGM-CGM-galaxies have proven critical to producing galaxy scaling
relations in cosmological simulations that match observations. However, the
nature of these processes, of the physics that drives outflows and accretion,
and their evolution with cosmic time are not fully characterized. One approach
to constraining these processes is to characterize the metal enrichment of gas
around and beyond galaxies. Measurements of the metallicity distribution
functions of CGM/IGM gas over cosmic time provide independent tests of
cosmological simulations. We have made great progress over the last decade as
direct result of a very sensitive, high-resolution space-based UV spectrograph
and the rise of ground-based spectroscopic archives. We argue the next
transformative leap to track CGM/IGM metals during the epoch of galaxy
formation and transformation into quiescent galaxies will require 1) a larger
space telescope with an even more sensitive high-resolution spectrograph
covering both the far- and near-UV (1,000-3,000 \AA); and 2) ground-based
archives housing science-ready data.
