First hi and welcome. This thread is 6 years old so you might not get a lot of replys. Metal polish tends to dry on the blade so I couldn't see it protecting to well and it is also abrasive so every time you cleaned it off you would be removing small amounts of metal and this could affect you edge. Some from memory also have chemical agents that may effect the edge and either way would affect etching and goldwash etc. Simple petroleum oil like baby oil is a much better option.