The electron dynamics in metals are usually well described by the semiclassical approximation for long-lived quasiparticles. However, in some metals, the scattering rate of the electrons at elevated temperatures becomes comparable to the Fermi energy; then, this approximation breaks down, and the full quantum-mechanical nature of the electrons must be considered. In this work, we study a solvable, large-N electron-phonon model, which at high temperatures enters the non-quasiparticle regime. In this regime, the resistivity either saturates at a value of the order of the quantum of resistance, or grows linearly with temperature without bound. Both behaviors are observed in different metals. We study the propagation of quantum chaos in the non-quasiparticle regime, and its relation to the thermal diffusivity.