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We have studied the dewetting of thin liquid metal films (Au, Cu, Ni) on fused silica substrates which occurs after melting with a Q-switched laser pulse. Optical microscopy, scanning electron microscopy, and scanning near field acoustic microscopy reveal two distinctly different modes of the dewetting process: On one hand, we observe heterogeneous nucleation of “dry” circular patches, which grow in diameter during the melting period. On the other hand, an instability of the liquid film against the growth in amplitude of surface waves with a characteristic wavelength is observed, which we believe is the first observation of spinodal dewetting. In contrast, the final structure of the ruptured film depends on whether nucleation or spinodal dewetting is dominant.