DAX (Data Analysis Expressions) plays a critical role in Power BI consulting by enabling consultants to perform advanced calculations and build custom measures in reports. DAX allows consultants to create dynamic, interactive visuals that respond to real-time data. It’s used to define relationships between datasets, generate time-based calculations, and apply complex business rules. Mastering DAX is essential for creating meaningful insights and driving data-driven decision-making. A Power BI consultant leverages DAX to turn raw data into actionable intelligence, improving the overall utility of reports for business users.