Many companies are now reporting on sustainability as a supplement to financial reporting. They are communicating their commitment to Environmental, Social, and Governance (ESG) programs. The data center industry has unique characteristics, such as high energy intensity, rapid growth, large power consumption and water usage that require specialized metrics. Standardizing these metrics will help with adoption, improve benchmarking, and progress sustainability within the industry. We propose five categories, which include 23 key metrics for data center operators who are in the Beginning, Advanced and Leading stages of their sustainability journey. We also identify the 17 most relevant sustainability frameworks and standards to guide data center operators in target setting, reporting, and certifying.