Periodic exchange of money between longs and shorts, AKA "funding".

If the contract price is above the price of the physical good, holders of the contract ("longs") pay the sellers of the contract ("shorts") a small fee every few hours.

This makes it less valuable to hold the contract, and pushes the price of the contract down, until its on par with the price of the physical good.

Through "funding". If the perpetual future's price is above (below) spot's price, long holders pay (receive) short sellers an interest at a regular interval (every 8 hours at most crypto exchanges).

Pay a fee to maintain the contract. Must post collateral if price moves against you or get liquidated.