There's an episode of Buffy The Vampire Slayer called Graduation Day, in which Buffy cures Angel (the vampire she loves) by feeding him her blood. He's sick, has little control, and together they collapse as he drinks at her neck in a frenzy. Angel, I should add, falls between Buffy's thighs. As he drinks, she grabs a metal jug that tumbled during the struggle and, being a girl with super-strength begins to crush it -- a sign of the torment she's in. Her fingers indent the metal, deforming it, squeezing it down.
Of course, it's widely accepted that the vampire motif represents, in part, the carnal side of desire; and Whedon and team play on this brilliantly. Safe to say the scene is intentionally erotic. Hell, it's downright suggestive. But the sexiest action, in my opinion, is the crushing of the jug. The teeth on the neck? Well, yes. The fact he falls on her in such a position? Obvious stuff. But her hand crushing that metal jug? It communicates an extreme and it does so through action, which is why, I argue, it has such a potent effect.
The reason I'm yabbering on about this (ooh, the spell check doesn't like that,) is because I recently read an erotic story by a writer unknown to me. I'm not going to rat on her -- the story wasn't so bad -- and suffice it to say the book will have sold well. But what snapped me out was how often she focused on object. She referred to what was being touched over and over again, and regularly spotlighted how that object felt. (Nipples hardening, that kind of thing). Here's my take: The arching of a spine, the clutching of a sheet, the rolling of a body -- these make a scene erotic. And if these movements can also suggest sensation... well, you're sold.
So, out of the following simple sentences, which is more sensuous?
"His hand was on my thigh."
"His hand moved up my thigh."
"His hand slid up my thigh."
My thoughts: The first achieves no movement and hardly any sensation. The fact the last two put the stress on the verb, providing a sense of movement, makes them more effective. But in the final one, the verb provides not only movement but also sensation. That's what makes it more apt. We're focused in on the action because the verb does so much work.
On a similar rant, when you use a cliche you immediately snap out the reader. So describing a climactic moment as a bursting dam, just serves to make me giggle. Not only has it been used too many times, but it also relies on exaggeration to communicate an extreme -- never could a climax be truly akin to a bursting dam. (If it were, we'd have to call the fire brigade or something. Snort.)
This is why Buffy's hand, as it squeezes the metal jug, is sexier than naming a body part. It shows rather than telling; it communicates sensation; it takes us to an extreme without the use of cliche.
And darn, it works.
P.S. It just occurred to me to add that context is important too. Sometimes "His hand was on my thigh" is far preferable to the others because it suits the context.