We performed molecular dynamics simulations of Zr50Cu50 metallic glass samples submitted to mechanical deformation at different strain rates. The simultaneous measurements of the stress–strain curve, and of the temperature evolution during the cyclic mechanical load, are used to determine the thermo-mechanical constitutive laws at the continuum scale. It is shown that plastic deformation acts as a heat source, but strong finite size effects affect the unfolding of shear bands and its related dissipation rate. Finally, a thermo-mechanical constitutive law is proposed to reproduce quantitatively self-heating processes at different scales.