Power-conversion efficiencies of solar cells based on halide perovskite (HaP) crystals have improved at a record speed and are currently above 24%, which pushed these systems to the forefront of materials, energy and nanoscience. It is both fundamentally and technologically important to understand phenomena that contribute to, or limit, the impressive optoelectronic performances of HaP-based devices. When examining charge-transport and light-absorption properties in a semiconducting material, a lattice of ions that are displaced from their equilibrium positions only by harmonic vibrations is typically invoked. However, a plethora of recent studies suggest that this picture is not sufficient to understand the properties of HaPs, in which different structurally dynamic effects, going beyond small harmonic vibrations, occur already at room temperature. After providing an introduction to HaPs and optoelectronic devices made from them, I will present our recent findings on the structural dynamics in these materials, using density functional theory and molecular dynamics calculations. Starting from the canonical band structure picture, theoretical and experimental findings on the impact of low-energy optical phonons and dynamic polar distortions in the mechanically soft HaP lattice will be discussed. I will use this to address open questions related to the charge-carrier dynamics in these crystals and related devices.