Thin metal films on flexible polymer substrates (foils) are used widely in satellite missions as they show extreme thermal isolation and high interface strength. Here, we show nanoscale “metafoils” with plasmon resonances, allowing interplay with visible radiation while reflecting the unwanted infrared responsible for device heating. The nanomechanical design of metafoils results in crack-free nanodomains, leading to resilient optical resonances withstanding strains up to ∼20%. We perform nanoscale electromagnetic and mechanical simulations to evaluate the metafoils’ mechano-optical behavior. Our simulations well fit the experimental positions of strain localization, resulting in material damage. The central nanodomains of metafoils remain crack-free at strains exceeding the crack offset strain of unpatterned foils by >84%. Fragmentation tests show that the crack spacing in metafoils can be tailored, in contrast to unpatterned films, by choosing appropriate structural parameters. Such small-footprint, resilient, and lightweight devices are highly desirable for heat rejection, communications, and spectroscopies in harsh environments.