There are dozens of things which you can measure in DevOps. But, primarily you can categorize those into three categories.
Efficiency: These are more of internal measures with respect to technical progress, product pipeline, and resource consumption. These are inside-out measures of efficiency and resource consumption (cost/time/materials) (Lead Time, Process Time, WIP)
Effectiveness: These are more of external measures with respect to quality, usefulness, performance, and business outcomes. These are outside-in measures of effectiveness and value delivered
Culture: Objective and subjective trends in team dynamics, process overhead, trustworthiness, shared objectives, morale, motivation, and team/product/enterprise identity