I think you are getting at gold lease rates, which equal the intrinsic interest rate of gold minus the cost of money (usually 30d Treasuries).
Currently, 30 day gold lease rates are in contango and equal to .096% APR for 30 days.
So, if you have an ounce of gold at $550, and 'loan' that gold out for one year, you would receive $550 x .00174*12= $11.48. At the end of the year you receive that gold back. You can't sell it until you get it back, unless you unwind the loan and pay the spread, right?
Does that answer your question?
insurance and storage of the physical metal would be extra.
See, and they told you (incorrectly) that physical metals don't have an interest rate.
Of course, unless you are a central bank or a major player & trading size, it is probably not that important.