We report the formation of microtower structures, observed on multishot nanosecond laser irradiation of liquid metals (Ga, In, Sn–Pb alloy, Wood’s metal). Ablation in a reactive ambient gas (air, nitrogen, sulfur hexafluoride, nitrogen trifluoride) is shown to lead to a tower-like structure growing on the irradiated surface at a rate of 3–20 μm per pulse depending on laser fluence and the types of metal and ambient gas. The interplay between different processes in the heat-affected zone of the irradiated samples is analyzed, including ablation, thermal expansion, temperature variations of viscosity, surface tension, thermal stresses, capillary effects, and surface chemistry. A clear picture of microtower origin has been established, and qualitative modeling can explain the formation mechanism. PACS 79.20.Ds - 42.62.-b
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