Holding cost refers to the interest cost of buying the underlying assets in the spot market and holding them in the future. Holding income is the income generated by the basic assets during the holding period. Therefore, the futures price should be equal to the spot price plus the cost minus the holding income. If we don't set the price in this way, trading futures will generate arbitrage opportunities.
The futures price and spot price of a specific commodity or financial instrument are restricted and influenced by the same economic factor, so their changing trends are roughly the same; Moreover, the spot price and futures price have convergence in the trend, that is, when the futures contract approaches the expiration date, the spot price and futures price will gradually converge.