From Wikipedia:
Tull returned strongly with 1987's Crest of a Knave. With Vettese absent (Anderson contributed the synth programming) and the band relying more heavily on Barre's electric guitar than they had since the early 1970s, the album was a critical and commercial success. Shades of their earlier electronic excursions were still present, however, as three of the album's songs again utilized a drum machine. The band won the 1989 Grammy Award for Best Hard Rock/Metal Performance, beating the favorite Metallica. The award was particularly controversial as many did not consider Jethro Tull hard rock, much less heavy metal. Under advisement from their manager, who told them they had no chance of winning, no one from the band turned up to the award ceremony.[1] In response to the criticism they received over the award, the band then took out an advert in a British music periodical with the line, "The flute is a heavy, metal instrument!".