This paper concisely summarizes and critically reviews recent work by the authors on models of the heating of the solar corona by resonance of ions with high-frequency waves (up to the proton cyclotron frequency). The quasi-linear theory of pitch angle diffusion is presented in connection with relevant solar wind proton observations. Hybrid fluid-kinetic model equations, which include wave-particle interactions and collisions, are derived. Numerical solutions are discussed, representative of the inner corona and near-Sun solar wind. A semi-kinetic model for reduced velocity distributions is presented, yielding kinetic results for heavy ions in the solar corona. It is concluded that a self-consistent treatment of particle distributions and wave spectra is required, in order to adequately describe coronal physics and to obtain agreement with observations.