Short answers, pulled from the story.
The Monterrey metropolitan area includes thirteen distinct municipalities in Nuevo León. These local governments are Apodaca, Cadereyta Jiménez, El Carmen, Escobedo, García, Guadalupe, Juárez, Salinas Victoria, San Nicolás de los Garza, San Pedro Garza García, Santa Catarina, and Santiago.
Official estimates from 2020 placed the population at 5,341,177 inhabitants. This figure makes it the second-largest metropolitan area in all of Mexico by headcount.
This region serves as a major industrial and economic hub for the entire country. Factories and corporate headquarters cluster within the boundaries of municipalities such as Escobedo and García to drive national production figures for steel, automobiles, and manufacturing goods.
Three adjacent towns do not maintain continuous urban development with the core yet remain vital to future plans. Ciénega de Flores, General Zuazua, and Pesquería share similar positions on the periphery of the existing city limits.
The conurbation evolved from its founding to become the modern urban center it is today through the steady merging of independent towns. Over decades, places like Guadalupe and San Nicolás de los Garza expanded their borders to meet the central city until they formed a single statistical entity recognized by INEGI statistics.