The Vale do Aço Metropolitan Region was established on 30 December 1998 and formally designated as a metropolitan region on 12 January 2006. Four municipalities form its core: Ipatinga, the largest and most industrial; Coronel Fabriciano, the historical seed city that older residents still call the cradle of the valley; Timóteo, home of the Aperam stainless works; and Santana do Paraíso, the smaller and newer municipality where the regional airport now sits. Twenty-four additional municipalities make up the metropolitan belt, including Caratinga - the most populous of the outer ring, its economy driven by coffee cultivation. A 2019 study by geographer William Passos identified the Vale do Aço as having the most significant metropolization of any interior region of Brazil's Southeast outside of São Paulo state.

The valley has grown in the shadow of Usiminas since the company's founding in the 1960s. Planned housing complexes went up in Ipatinga and Timóteo to accommodate the industrial workforce - entire neighborhoods designed on a grid, named for engineers, built to absorb the steelworkers and their families. But the planning could not absorb everyone. The 1964 separation of Ipatinga and Timóteo from Coronel Fabriciano took tax revenue with the steel plants, leaving Fabriciano without the resources to match its growing population. Slums - called favelas - grew on the unstable hillsides, particularly in Timóteo, where land was occupied faster than it could be serviced. The valley's prosperity has never been evenly distributed. The steelworkers inside the factory gates and the families pressed onto the red-dirt slopes above them share a skyline but not much else.

In the early 2010s, demand for steel declined in both domestic and international markets. The layoffs hit the Vale do Aço hard. Industrial jobs disappeared between 2011 and 2013 across all four core municipalities. Ipatinga alone recorded thousands of layoffs across all sectors between January and March 2015, most of them in construction, as the ripple from the steel downturn passed into the commercial and service economies. By December 2015, the Ipatinga city administration had suspended 25% of its commissioned positions. The valley had built itself around a single industry and found out what happens when that industry softens. Recovery has been partial. Caratinga, in the metropolitan belt, has seen coffee cultivation and local commerce hold up better than steel.

The four core cities have a Human Development Index for longevity above both state and national averages. Life expectancy at birth in Coronel Fabriciano and Ipatinga is 76.8 years; in Santana do Paraíso, 77.6. The Márcio Cunha Hospital in Ipatinga - managed by the São Francisco Xavier Foundation, a Usiminas philanthropic arm - is the regional reference for high-complexity care including oncology and hemodialysis. The Catholic University Center of Eastern Minas Gerais, Unileste, was established in 1969 and has campuses in Coronel Fabriciano and Ipatinga. It remains the largest educational complex in eastern Minas Gerais, producing engineers, doctors, and teachers for a valley that needs all three. In 2010, 14.5% of the metropolitan population was enrolled in higher education.

For all the steel and smoke, the Vale do Aço sits within easy reach of some of the best-preserved Atlantic Forest in Minas Gerais. The four core cities belong to the Atlantic Forest Tourist Circuit, established in 2001 to promote ecological and cultural tourism. The Serra dos Cocais offers waterfalls and hiking; Rio Doce State Park protects one of the largest remaining patches of the biome. Serra da Viúva, in Santana do Paraíso, hosts the José Paulino dos Santos Hang Gliding Ramp, a reference point for the sport that draws practitioners from other Brazilian states and from abroad. The Usipa Sports and Recreational Association in Ipatinga - built by Usiminas - includes a heated Olympic-size swimming pool, multiple courts and fields, an athletics track, and a zoo. The valley that makes steel also, on the weekends, plays.

From cruising altitude the Vale do Aço unfolds as an urban corridor along the Piracicaba River, running west-east through the heart of eastern Minas Gerais, with the bulk of the industrial activity clustered in Ipatinga where the Usiminas plant dominates the northern bank. Plumes from the steelworks rise on calm days. To the east, the Doce River valley opens toward the coast; to the west, the uplands climb toward Belo Horizonte. The four main cities form a broadly continuous urban fabric that reads, from the air, as one large metropolis rather than four separate municipalities - which is precisely the point of the metropolitan region designation.