In Spot Bullion (Gold/Silver) trading, there is an element known as swap, or commonly known as rollover charge. Bullion swaps are debited/credited when a bullion position is held to the next day. Spot Bullion trade involves borrowing a funding currency (e.g. USD) to pay for Gold/Silver, or borrowing Gold/Silver to pay for the funding currency. The differential between the Bullion lease rate and the funding currency interest rate that you trade in would therefore determine the bullion swap.