Megacities: Megacities are cities with a population of over 10 million. The Philippines doesn't have any megacities. The highest populated city in the Philippines is Quezon City with a population of only 2,960,048.
Metacities: The AMSCO textbook states, "Metacities, sometimes called hypercities, are defined in two ways: • continuous urban area with a population greater than 20 million people • attributes of a network of urban areas that have grown together to form a larger interconnected urban system" The Philippines doesn't have any metacities.
Megalopolis: The AMSCO textbook states, "The term megalopolis goes back to the early 1900s and describes a chain of connected cities." Mega Manila is a megalopolis. Wikipedia states, "Mega Manila is a megalopolis on the island of Luzon, Philippines. There are varying definitions of the megalopolis, but it is generally seen as encompassing the administrative regions of Central Luzon, Calabarzon, and Metro Manila. On some occasions, the administrative region of Mimaropa is also included" (Mega Malina).