Marc Bolan, 29, a British musician who became a rock star as leader of the heavy metal rock band T-Rex., died Friday in a car crash in a London suburb.

The singer-guitarist, who recently made a comeback from alcoholism and drug addictions, was killed when a car, driven by his girl friend, Gloria Jones, an American singer, crashed into a tree. Jones was injured but is reported to be in good condition.

Mr. Bolan, who was born Mark Field, was not driving the car because he refused to learn how to drive, fearing that he would die young in a car crash, according to his former manager, Tony Secunda.

Mr. Bolan left the rock music world in 1975, afflicted with several drug dependence, he acknowledged in an interview two weeks ago. Between the late 1960s and 1975, he had made 20 hit records and signed a $1.75 million recording contract.

" . . . I cracked up," he said in the interview. "I was living in a twilight world of drugs, booze and kinky sex.

"At my peak, I was drinking a bottle (of brandy) or more a day as well as wine. I was sniffing cocaine and taking all sorts of pills . . . I knew Elvis, Jimi Hendrix and Brian Jones and they all cracked up. I don't want to go the same way."

Bolan, who became the first British rock sensation on the British music charts since the Beatles and David Bowie, first gained notoriety as an idol for teeny boppers. In the late 1960s he began doing heavy rock and staged his act in a high-camp style that included heavy makeup, eye shadow, glitter in his hair and rainbow-colored silk clothes.

Bolan, who at one time claimed to have had a number of homosexual relationships, recently began a new career introducing a children's television show in Britain. He was preparing to make new tours with his group.

In the wreckage of the car in which Bolan was killed, witnesses reported that there was an entertainment newspaper open to the headline:

"Hope I Grow Old Gracefully Before I Die."