Methods for forming an enclosed liquid metal (LM) drop inside a sealed cavity by formation of LM components as solid LM component layers and reaction of the solid LM component layers to form the LM drop. In some embodiments, the cavity has boundaries defined by layers or features of a microelectronics (e.g. VLSI-CMOS) or MEMS technology. In such embodiments, the methods comprise implementing an initial microelectronics or MEMS process to form the layers or features and the cavity, sequential or side by side formation of solid LM component layers in the cavity, sealing of the cavity to provide a closed space and reaction of the solid LM components to form a LM alloy in the general shape of a drop. In some embodiments, nanometric reaction barriers may be inserted between the solid LM component layers to lower the LM eutectic formation temperature.