The price of West Texas Intermediate (WTI) Crude Oil contracts for May 2020 delivery just closed at -$37! In other words, those who want to "buy" oil in May will be paid $37/barrel by the oil "sellers." We never expected to see negative oil prices until the past several weeks, as the capacity to store oil has dwindled and there are high costs to stopping oil extraction. Although prices for May delivery dropped below zero today, prices remain positive (at this point in time) for June and future delivery dates.
Like negative interest rates, the negative price of oil is a good reminder that there are non-financial factors to consider when investing. Negative interest rates are indicative of non-economic buyers of fixed-income assets (such as central banks, index funds, trading partners, etc), while negative oil prices represent the physical limitations certain markets. Understanding the financial or physical mechanics of investments is often just as important as understanding the traditional economics of an asset class itself.