NO. Only things with charged particles are affected by magnetic fields. Mesons have no charge so they're unaffected.
Magnetic armor would be useful against plasma guns and fusion guns since those are essentially bolts of ions. It would also work against HEAP warheads.
Paricle beam weapons no. Charged particle beams,yes. But a space-to-space PBW has got to have a neutral charge or repulsion would blow the beam apart before it goes 100 km
Lasers no No electric charge on light.
Missiles maybe, probably not The given enough megawatts the mangnetic field could be manipulated to jam the guidance and fuse, but only in the last microsecond, probaably not quick enough to do any good.
Nuclear weapons no. The radiation is mostly neutrons (D-T reactions) or photons (D-T converted to X-rays, or p-p) neither is affected by magnetic fields.
Gauss Weapons yes The projectile is magnetic in Traveller rules.
Chemical projectie weapons no Most APDS or APFDS projectiles are non-magnetic tungsten or DU. HE shells are unmagnetized iron.
Solar flares, yes.