Magnetic fields act on all moving charges.
The force induced by a magnetic field always acts perpendicular to both the velocity of the particle and the magnetic field itself. The force is based on the charge of the particle, its velocity, and the strength of the magnetic field. To find the direction of the force, first point your finger tips in the direction of the velocity of the charge. Then close your fingers through a 90 degree arc so that they point in the direction of the B-field. Keep your thumb extended while doing this.