  We present some of the salient aspects of the scientific motivation for high
resolution soft X-ray spectroscopy of early-type stars with the Line Emission
Mapper X-ray Probe. The major strength of {\it LEM} for hot star physics is its
large effective area, aided by the inherent energy resolution of its
microcalorimeter that readily achieves resolving powers of 1000 and obviates
the need for relatively inefficient dispersive optical elements. This increased
sensitivity enables much fainter and more distant high mass stars to be
observed than are accessible with present-day facilities, greatly increasing
the pool of potential targets. For brighter sources, the sensitivity opens up
time domain studies, wherein sufficient signal can be garnered in short order
and exposure times, probing source variations on ks timescales. We argue that
these capabilities of {\it LEM} will yield breakthroughs in all types of hot
star systems, from understanding single OB and WR star winds and how they vary
with metallicity, to probing the shocks of colliding wind systems and the
magnetically channeled winds of magnetic OB stars. {\it LEM} will also study
the energetics of WR star bubbles and feedback from their powerful pre-SN
stellar winds.
