The large-scale magnetic fields are of paramount importance for the cosmic ray astrophysics. Patterns in the motion of interstellar medium may provide some constraints on the structure of galactic magnetic fields, especially in our Galaxy. It seems that magnetic fields cannot be ignored in attempts to fully address the problem of the rotation of spiral galaxies. The interstellar gas is ionized to a degree sufficient for the magnetic field to freeze-in the gas, so that the resulting magnetic tension influences its motion, modifying the predictions of purely gravitational models of galactic rotation. The inclusion of magnetic fields has implications for the predicted local mass-to-light ratio and so might help to reduce the missing mass problem.