  The convective envelopes of cool main-sequence stars harbour magnetic fields
with a complex global and local structure. These fields affect the near-surface
convection and the outer stellar atmospheres in many ways and are responsible
for the observable magnetic activity of stars. Our aim is to understand the
local structure in unipolar regions with moderate average magnetic flux
density. These correspond to plage regions covering a substantial fraction of
the surface of the Sun (and likely also the surface of other Sun-like stars)
during periods of high magnetic activity. We analyse the results of 18
local-box magnetohydrodynamics simulations covering the upper layers of the
convection zones and the photospheres of cool main-sequence stars of spectral
types F to early M. The average vertical field in these simulations ranges from
20 to 500G. We find a substantial variation of the properties of the surface
magnetoconvection between main-sequence stars of different spectral types. As a
consequence of a reduced efficiency of the convective collapse of flux tubes, M
dwarfs lack bright magnetic structures in unipolar regions of moderate field
strength. The spatial correlation between velocity and the magnetic field as
well as the lifetime of magnetic structures and their sizes relative to the
granules vary significantly along the model sequence of stellar types.
