A Metro Manilan is, of course, someone that is currently located in, originated from, or is somehow associated with Metro Manila.
Metropolitan Manila, commonly known as Metro Manila or simply Manila, is the official and administrative definition of the urban area surrounding the Philippine capital city, Manila. It is the capital region of the Philippines, the seat of government, and the second-most populous and most densely populated region of the country. Also officially known as the National Capital Region (NCR), it is composed of the City of Manila, Quezon City, the country's most populous city, and the cities of Caloocan, Las Piñas, Makati, Malabon, Mandaluyong, Marikina, Muntinlupa, Navotas, Parañaque, Pasay, Pasig, San Juan, Taguig, and Valenzuela, including the only remaining municipality of Pateros. - Wikipedia