You don't always have to be a couple or single female to be invited to a swinging party, some do invite single males. There are lots of nice single men on here who get to go to parties. You might want to chat on the forum or in the chatroom abit and get yourself known, that's more likely to result in you getting invited to parties or fitting the criteria for attending a munch (see left of this page for the definition of a munch).
Hope that helps.
Its true once you get yourself known people will invite you, thats if your nice.
MikeC