When copper metal is placed in a silver nitrate solution, a silver metal coating forms on the surface of the copper. This is a classic example of a single displacement reaction.

Here's the breakdown:

* Copper (Cu) is more reactive than silver (Ag).

* In the solution, silver nitrate (AgNO₃) exists as silver ions (Ag⁺) and nitrate ions (NO₃⁻).

* The copper atoms donate electrons to the silver ions, causing the silver ions to reduce and become solid silver metal.

* The copper atoms oxidize and become copper ions (Cu²⁺) which then dissolve into the solution.

The chemical reaction is:

Cu(s) + 2AgNO₃(aq) → 2Ag(s) + Cu(NO₃)₂(aq)

In summary: The substance formed on the copper metal surface is solid silver metal (Ag).