High-velocity clouds (HVCs) around the Milky Way provide direct evidence of ongoing gas accretion that could fuel the future star formation activity of the Galaxy. Whether the clouds are capable of delivering cold gas to the Galaxy depends on whether they survive their passage through the hostile circumgalactic gas environment. Theories and numerical simulations predict that the magnetic field significantly affects the efficiency of the mixing at the cloud-halo interface, which could in the long run affect the survival of the clouds. My thesis focuses on laying the groundwork for the rapidly emerging era of magnetism study using radio polarimetry and provides a glimpse of what will be possible in the near future. From an observational standpoint, I evaluate conditions for the detection of magnetized circumgalactic clouds using Faraday rotation measure (RM) observations of extragalactic polarized radio sources. From a theoretical standpoint, I investigate how the evolution of circumgalactic clouds is interconnected with the presence of magnetic fields.