Among many physical processes involved in star formation, radiation transfer is
one of the key processes since it dominantly controls the thermodynamics.
Because metallicities control opacities, they are one of the important
environmental parameters which affect star formation processes. In this talk, I
will report the results of 3D radiation magnetohydrodynamic simulations of
protostellar collapse in solar-metallicity and low-metallicity ($Z = 0.1
Z_\odot$) environments. Because radiation cooling in high density gas is more
effective in the low-metallicity environments, first cores are colder and have
lower entropies. As a result, first cores are smaller, less massive and have
shorter lifetimes in the low-metallicity clouds. Therefore, first cores would be
less likely to be found in low-metallicity star forming clouds. This also
implies that first cores tend to be more gravitationally unstable and
susceptible to fragmentation. The evolution and structure of protostellar cores
formed after the second collapse weakly depend on metallicities in the spherical
and magnetized models despite the large difference in the metallicities. On the
other hand, the effects of different metallicities are more significant in the
rotating models without magnetic fields, because they evolve slower than other
models and therefore more affected by radiation cooling.