Yes, plastering can be done on metal surfaces, but the surface must be properly prepared to ensure good adhesion. The metal surface should be cleaned of any dirt, rust, or other contaminants and may need to be primed with a bonding agent to help the plaster adhere.  Additionally, the type of plaster used for metal surfaces may need to be specifically formulated to accommodate any expansion or contraction of the metal due to temperature changes. It is important to follow the manufacturer's instructions and consult with a professional if unsure about the appropriate plastering method for a metal surface.