From the passage provided, extract the  population of Seattle metropolitan area

Seattle (/siˈætəl/ (listen) see-AT-əl) is a seaport city on the West Coast of the United States. It is the seat of King County, Washington. With a 2020 population of 737,015,[2] it is the largest city in both the state of Washington and the Pacific Northwest region of North America. The Seattle metropolitan area's population is 4.02 million, making it the 15th-largest in the United States.[10] Its growth rate of 21.1% between 2010 and 2020 made it one of country's fastest-growing large cities.[11]

The Seattle metropolitan area's population is 4.02 million, making it the 15th-largest in the United States