Here are some of the most frequently used DAX (Data Analysis Expressions) functions in Power BI:

- SUM: calculates the sum of a set of values
- AVERAGE: calculates the average of a set of values
- COUNT: counts the number of items in a set
- MIN: returns the minimum value in a set
- MAX: returns the maximum value in a set
- IF: returns one value if a condition is true and another value if itâ€™s false
- TODAY: returns the current date
- NOW: returns the current date and time
- LEFT: returns a specified number of characters from the start of a text string
- RIGHT: returns a specified number of characters from the end of a text string

These are just a few of the many DAX functions available in Power BI, and the specific functions you use will depend on your data and analysis requirements.