What do we talk about when we talk about sculpture? Not pounds or kilograms, for sure. It hardly deepens our view of Giacometti’s spindly figures or Calder’s light-as-air mobiles, or even the pioneering brown-hued “Guitar” that Picasso assembled from sheet metal, to know they weigh, say, 50 or 60 or 100 pounds.

But Richard Serra, unlike his modernist forebears, counts pounds. “This is my heaviest show ever,” he said with a hint of pride, when we met recently in his studio. It was an August weekend, and the streets of TriBeCa, where he lives and works in a six-story brick building, had emptied out. The 80-year-old artist was preparing for a somewhat crazed fall season. Three exhibitions of his new work will open simultaneously, in mid-September, at the Gagosian Gallery’s spaces in Chelsea and on the Upper East Side.

Add to that the unveiling of a not-slight piece at the Museum of Modern Art. “Equal” (2015), a room-sized assembly of eight, 40-ton forged-steel blocks that together weigh more than a Boeing 777 , will occupy its own gallery in the new David Geffen Wing when the museum reopens on Oct. 21.

Mr. Serra, the best-known living sculptor in America, might seem out of step with our increasingly virtual world. In an age when visual satisfactions scroll by on Instagram in seconds, he revels in the physical — enshrining abstract forms as maximalist feats of mass and scale. Tellingly, his medium is steel, whose production in this country peaked in the middle of the 20th century.