1. Modern dance, a "pure" art form divorced from plot, character, and political-social context (though she choreographed many plot-driven ballets, too).
2. An emphasis on the male form, a solid muscularity and blatant eroticism, often with homoerotic implications (asked how a woman could depict masculinity so well, she replied "I like men").
I recommend El Penitente (1940), Night Journey (1947), Episodes (1974), and The Rite of Spring (1984).
But she didn't always emphasize maleness. When she founded the Martha Graham Dance Company in 1926, it was female only. In 1939, she drew 30-year old Erick Hawkins away from George Balanchine's American Ballet and Ballet Caravan, making him her first male dancer, the centerpiece of many performances.
And her lover, although he was 15 years younger and bisexual, leaning more toward men (maybe she found him intriguing because, according to rumor, he had one of the largest endowments in the dance world).
They married in 1948.
Erick often emphasized muscular male bodies -- perhaps because, like Martha Graham, he "liked men."
He continued to perform well into his 70s.
See also: Ted Shawn, a pioneer of male dance.