Vk bands dress in a feminine manner but can have many styles. Malice Mizer had more of a romantic/gothic/1800's feel whereas Dir en grey had a more of a slutty, vinyl miniskirts and thigh-high bitch boots style. Kagrra does more traditional clothing like colorful kimonos and Psycho le Cemu is just plain messed up with schoolgirl uniforms and outfits that look like cheap halloween costumes.
VK rockers are generally NOT gay/bisexual. They dress like women to attract record deals, attention, and fans, however, after signing a major record deal and going "mainstream" they usually lose the visual look and become "normal".
Fans usually are females who love the look of the band members, so they like the music. Many VK bands sound the same.
Some VK bands are Duel Jewel, Malice Mizer, Psycho Le Mu, BLOOD.
The only good vk band is Dir En Grey, and that's because they no longer look like tranvestites.