Something that's never happened in the oil market is happening today: negative prices on an oil contract.

While many people may see this and think the overall price of oil is negative, there's nuance. The short answer is that no, not all oil is free.

The picture in the market is not as bleak as this eye-popping headline would suggest.

Futures contracts are tied to a specific delivery date. Toward the end of a contract's expiration date, the price typically converges with the physical price of oil as the final buyers of these contracts are entities like refineries or airlines that are going to take actual physical delivery of the oil.

Futures contracts ultimately are contracts for physical delivery of the underlying commodity or security. While some people in the market speculate on the contracts, others are buying and selling because they have use for the commodity itself. Near the contract's expiration, traders just start buying the next month's futures contract. Those who stay in the position to the final day are typically buying the physical commodity, such as a refiner.

The West Texas Intermediate crude contract that fell more than 100% on Monday is for May delivery, and it expires Tuesday. With the coronavirus pandemic leading to unprecedented demand loss, and with storage tanks quickly filling up, there is no demand for this oil contract expiring Tuesday.

That's why it turned negative, meaning producers would pay to get this oil off their hands because there is no one that needs that crude this week with the country shutdown.

Futures contracts trade by the month. The contract for June delivery was 16% lower at $21.04 per barrel.

So after the May contract expires on Tuesday, oil could be back above $20.