A novel thermal storage device includes a container of metallic phase change material (MPCM). The MPCM has a high latent heat of fusion and a high thermal conductivity in its solid state. A thermal energy receiver is adapted to receive thermal energy from a thermal energy source and transfer the thermal energy directly to the MPCM, without the need for an intermediate thermal transfer fluid. A thermal energy discharge mechanism transfers thermal energy directly from the MPCM to a device that uses the thermal energy. In a solar energy embodiment, the thermal energy receiver is formed from a material (e.g., polished copper) that has a relatively low absorptivity value and a relatively low emissivity coefficient, which unexpectedly results in the attainment of a highly efficient solar receiver.