<p>An experimental study of the directional (normal) emissivity of metallic aluminum, gallium, and indium is presented. The work was carried out due to the lack of reference data on the emissivity of gallium and indium, as well as to clarify the data on aluminum in an extended temperature range compared to previously published ones. The metals considered are widely used as component units of nuclear reactors. The data on gallium and indium are interpreted as having been obtained for the first time, and they are preliminary in nature, requiring further clarification. The measurement method is radiative, the method of heating samples is resistive. Experimental errors amount to ±5–8%. The temperature dependences of the directional (normal) emissivity of aluminum and indium in the solid and liquid states were investigated, including stepwise changes during the phase transition. The temperature dependence of the emissivity of gallium was studied only in the liquid state. The results of a comparative analysis of the physical experiment with the results of a computational experiment using the Foote approximation are presented. It is concluded that the theoretical calculation of emissivity allows for a qualitative, but not quantitative, description of the behavior of the emissivity of metals, provided that the values of the specific electrical resistance of the metals in the temperature range under study are known. The experimental results obtained are relevant for conducting heat engineering calculations.</p>