The Vamp is traditionally an Always Female trope, intimately connected to male-female power dynamics and feminine stereotypes and imagery. This is obviously not to say that men cannot be seducers or destructive to women in vaguely analogous ways, just that such tendencies will be expressed and depicted in differently coded cultural constructs—for example, a seductive man is likely to be dangerous in a more overtly predatory and physically threatening way.
However, in more recent fiction, feminine-presenting gay characters can sometimes play this role "straight" when paired with someone of their own sex. The glamorous Lipstick Lesbian who seduces a nice Proper Lady or innocent Girl Next Door for her own wicked ends has already become a stereotype, and the more fantastical Lesbian Vampire fits this trope too. For whatever reason, male examples are less common, but do exist. A male example might be an evil Camp Gay lover slowly destroying his manly man, or, if the mark is straight, a devious crossdresser who merely adds yet another layer of deception to the Vamp's usual manipulations by lying about his real sex. (Just as with a straight example—and possibly more so, given the prejudice that still remains in real life against gay people as predatory—such cases can of course have Unfortunate Implications if executed poorly.)
In a setting where true gender bending is possible, it's naturally even easier for a male villain to make himself a convincing Vamp, should he want to. This can also veer into transphobia (mostly against trans women), who often also get presented as "deceivers" that may trick straight men (which often overlaps with depictions of crossdressing gay men, due to the popular misconception that Trans Equals Gay).
