The spot price and the futures price for the same metal are separate numbers produced by separate markets. They track each other closely most of the time, and the exceptions are informative.
The two markets serve different purposes
Spot trading concerns metal available now, typically settling within a couple of days and usually involving bars in a recognised vault.
Futures are standardised contracts for delivery at a specified later date, traded on an exchange with margin, and most are closed out before delivery is ever due.
The participants differ accordingly. Refiners and jewellers dominate one; funds, banks and speculators dominate the other.
Arbitrage normally holds them together
If the futures price rises too far above spot, a trader can buy physical metal, sell the future and lock in the difference less carrying costs.
That trade is only worth doing when the gap exceeds storage, insurance and financing, so the two prices stay within a band rather than being identical.
The width of that band is set by how expensive it is to hold metal, which is why the gap widens when interest rates rise.
Delivery frictions can break the link
The arbitrage requires metal in the right form, in the right vault, in time to satisfy the contract. Any obstacle to that makes the trade impossible to execute.
Disrupted freight, closed refineries or bars of the wrong specification can all prevent physical metal from reaching the delivery point.
When that happens the futures price can detach from spot for as long as the obstacle lasts, sometimes by an amount that would be absurd in normal conditions.
Contract specifications matter more than they seem
Each futures contract defines an acceptable bar size, purity and set of approved vaults, and only metal meeting that definition can settle it.
Metal that fails the specification is still valuable, but it cannot close a futures position without being recast, which takes refinery capacity and time.
Episodes of extreme divergence have often come down to a shortage of the specific deliverable form rather than a shortage of the metal in general.
Rolling positions carries its own cost
A holder using futures for continuing exposure must close each contract before delivery and open the next one, paying whatever difference exists between them.
In an upward sloping market that roll costs money on each cycle, which accumulates over long holding periods.
Two investors can therefore hold the same metal exposure and record different results, purely because one held bars and the other held contracts.