S&P 500 indexes in May extended gains from April, with the broader S&P 500 index performing better than the S&P 500 Utilities and S&P 500 Energy indexes during the month.

The S&P 500 index saw a total return of 4.8%, according to S&P Global Market Intelligence data. Over the same period, the S&P 500 Utilities index posted a total return of 4.4%, and the S&P 500 Energy index recorded a total return of 1.9%.

ONEOK Inc. recorded a total return of 22.6% for the month of May. The company closed a $1.5 billion senior note offering composed of $600 million of 5.850% senior notes due 2026; $600 million of 6.350% senior notes due 2031; and $300 million of 7.150% senior notes due 2051.

During the company's earnings conference call, ONEOK management defended their decision to preserve the company's dividend by saying that deeper spending cuts should be enough to support it.

Baker Hughes Co. saw a total return of 19.8%. Chairman, President and CEO Lorenzo Simonelli said cost savings from reducing the company's headcount and manufacturing footprint, as well as cutting overhead costs, could drive around $700 million in annualized savings across the organization.

Halliburton Co. posted a total return of 11.9%. The oilfield services provider slashed its second-quarter dividend to 4.5 cents per common share, from 18 cents, and also laid off about 1,000 workers from its headquarters in Houston, as a result of the current market downturn.

Marathon Petroleum Corp. had a total return of 11.4%. President and CEO Michael Hennigan said the integrated oil refiner would scrutinize its assets and suggested that some might be placed on the block.

Schlumberger Ltd., which logged a total return of 9.8%, is considering overhauling the company by consolidating its multiple business segments into four divisions that will operate in five geographies, according to a report by the Houston Chronicle.

At the other end of the spectrum, Occidental Petroleum Corp. saw a negative return of 22.0% in May.

Struggling with immense debt and unsuccessful asset sales, Occidental slashed its quarterly dividend to 1 cent per common share, its lowest since the company began paying dividends in 1978. The company also reportedly engaged investment bank Moelis & Co. for advice on how to address its $40 billion debt load.

Apache Corp., with a negative return of 17.5%, notified the New York Stock Exchange and the Chicago Stock Exchange of its intent to voluntarily delist its shares from the exchanges in a bid to save costs.

Marathon Oil Corp. recorded a negative return of 12.7%. The company suspended its dividend and share buyback programs and is "hitting the pause button" on its operations in the Delaware Basin and Oklahoma in favor of the Eagle Ford and Bakken shales.

Among other bottom-performers, Devon Energy Corp. posted a negative return of 13.3% while TechnipFMC PLC saw a negative return of 16.9%.

Among the components of the S&P 500 Utilities Index, NextEra Energy Inc. saw a total return of 10.6% for the month of May. NextEra filed a petition with the Texas Supreme Court asking for a review of its failed $18.7 billion acquisition of Oncor Electric Delivery Co. LLC, claiming that state regulators overstepped their authority.

Dominion Energy Inc. reported a total return of 10.2%. The company sees about $9.9 billion in investment potential at its Virginia subsidiary through 2024 as it adds thousands of megawatts of renewables and storage to its generation mix.

On the flip side, AES Corp. posted a negative return of 5.7%. AES reduced the midpoint of its 2020 adjusted EPS guidance by 7 cents to a range of $1.32 to $1.42, primarily due to lower demand across its businesses, particularly at U.S. utilities.

NiSource Inc., with a negative return of 5.1%, lowered its 2020 capital investment plan by $100 million to a range of $1.7 billion to $1.8 billion, in order to conserve cash as a response to the coronavirus pandemic. Company executives said the pandemic could put downward pressure on the NiSource's 2021 earnings, which are already somewhat uncertain due to the sale of its Massachusetts gas distribution business.

Among other electric and diversified utilities, PPL Corp. saw a total return of 9.9%, Entergy Corp. booked a total return of 7.7%, and NRG Energy Inc. logged a total return of 7.5%. Meanwhile, Consolidated Edison Inc. had a negative return of 3.7%, and Edison International posted a negative return of 1.0%.