At age sixteen, in 1987, Debbie Gibson, of Merrick, Long Island, released her début album of original pop songs, “Out of the Blue,” which went triple platinum. At seventeen, she became the youngest artist in history to write, perform, and produce a Billboard No. 1 single; at eighteen, she tied Bruce Springsteen for ASCAP’s Songwriter of the Year. Before that, she was a fairly normal, if precocious, suburban kid. Recently, Gibson, now fifty-five, visited the Metropolitan Opera House, which plays a supporting role in her new memoir, “Eternally Electric.” Gibson, who is energetic and youthful, often sings snippets of songs (“Pink Pony Club,” “Copacabana,” “Raspberry Beret”) to illustrate points, and she zipped around in high-heeled sandals and a combo of biceps-flaunting sleeveless top and flared pants. “This is so incredible…