Simple answers are that they're cruising you on the dance floor, and perhaps without any other dance partner, hope you'll dance a little with them, so they don't have to dance alone. A lot of guys at the US clubs I've gone to would do that.
Story: when I would dance (and haven't in a few years now) the lights could trigger an epileptic seizure, especially when they strobe. So I wore sunglasses, which obviously reduced the light intensity, but also allowed me to close my eyes totally as needed, without it being obvious to others.
One time this really weird character started dancing next to me, known for always trying to hit on guys. He was dressed in bad drag, as he often did as a club regular, but without a wig, just his regular short male haircut. I didn't notice him.
But my partner did, who had left the dance floor to get us some drinks. When he came back he exploded, yelling at this guy if he ever came near his husband again he'd haul him outside into the parking lot and he wouldn't be coming back in one piece.
I was astonished, had never heard him sound off like that before. Nor had anyone else in the club, the dance floor almost coming to a standstill, actually scared me, and I hoped he wouldn't think I had anything to do with this. The other guy fled to the main bar, never approached me again. My hubby understood, knew how I danced blind, and I escaped his wrath. WHEW!!!
So my question for you, since your profile is silent, are you going to the club single or with a guy? If with a guy, do establish the protocols with him, the default mode being you usually dance with the guy who brung ya. But if you're alone, enjoy the attention, it's normal.