A week's visit from the Metropolitan Opera will open Wolf Trap's seventh season on June 6, it was announced yesterday.

The 12-week season, running through Aug. 28, also will include programs ranging from Country singer Tammy Wynette to the Joffrey and Martha Graham dance troupes, the tap-dance Hoofers, chamber music and the big-band sound of the '40s.

Christopher Hunt, Wolf Trap's new artistic director, said he even hoped to experiment this summer with legitimate drama on Wolf Trap's open-air stage. Sound difficulties with the spoken word have kept Wolf Trap from bringing theater to its program.

The opera offerings include six operas from the Met plus three productions staged by the Wolf Trap Opera Company.

This year, Hunt emphasized, the Met can't be accused of sending second-string casts on tour. He pointed to such stars as Renata Scotto, Elena Obraztsova, James McCracken, Marilyn Horne and James Levine, the Met's music director, who will conduct three of the performances.

The six operas from the Met include Puccini's "La Boheme" and "Tosca," Mozart's "The Magic Flute," to be performed in English at the matinee performance; Verdi's II Trovatore," and this season's new Met productions of "Lohengrin" and "Le Prophete."

For its own opera program, Wolf Trap will offer "Hansel and Gretel," Busoni's "Doktor Faust" in a multimedia staging by Frank Corsaro and Ron Chase, and Cavalli's "L'Egisto," with the sets and costumes from the much praised Santa Fe production of 1974.

Corsaro and Chase will use film shot on location in Europe as part of the multi-media staging of the Faust opera. For Cavalli's baroque pastoral romance, the cast will include Carmen Balthrop, the young Washington soprano who was so stunning in voice and figure in "Treemonisha."

"We need an attractive cast because the costumes are extremely scanty," Hunt observed dryly.

Among the popular entertainers for Wolf Trap's summer will be the Starland Vocal Band, the locally-based group that won a Grammy last week as the best new artist(s) in the pop music field.

There also will be performances by the Wolf Trap sell-out favorite, the Preservation Hall Jazz Band. The jazz musicians will be double-bilied for one performance with tap-dance Hoofers.

For "Nostalgic Sounds From the Summer of '42," there will be Tex Beneke and His Big Band with vocalists Helen O'Connell and Bob Eberly.

In concerts, Raymond Leppard will direct three baroque concerts, including all six of Bach's Brandenburg concerti and Handel's "Water Music" and "Fireworks Music," the latter scheduled appropriately for July 3.

There also will be an all-Mendelssohn night, Aaron Copland conducting an evening of his own music, and Julius Rudel continuing the Mahler cycle with the Fourth Symphony.

The Guarneri Quartet will offer an all-Beethoven evening, and there will be recitals by Jean-Pierre Rampal, Earl Wild and Carlos Montoya.

For dance, Wolf Trap will bring five companies to its stage - Martha Graham, Eliot Feld, Joffrey Ballet, Erick Hawkins, and the London Contemporary Dance Theater on its first trip to America.