A Power BI consultant plays a critical role in integrating external data sources by connecting Power BI to a variety of platforms, including SQL databases, cloud services, ERP systems, and CRM tools. They ensure seamless data flow from these sources into Power BI, providing a unified view of business data. Consultants handle data transformation and cleaning processes, ensuring consistency and accuracy. Their ability to integrate multiple data streams enables organizations to conduct comprehensive analysis, uncover insights from previously siloed information, and make data-driven decisions based on a holistic view of the business.