I did an MMF threesome a few years ago. It took a lot of arranging but we finally did it.
Up until then I'd been entirely gay and not had much interest in women, but all the horny chat and pics beforehand got me super turned on and a little 'straight curious'.
Their deal-breaker was: They first wanted me to fuck him while she watched. Apparently they had a few guys saying they'd do it, but then bottle it at the last minute, or only be interested in her. Anyway, only too happy to do anything with him!
We met up in a little bar not far from their place. Some chat and a couple of drinks, then he reached under the table and started rubbing my crotch through my pants. (They mentioned they were going to want to see if he would get me hard before going back to their place.) I was wearing just loose sweatpants with no underwear and soon got very hard. Then he slipped a hand inside and checked out my goods. While we were talking, he took her hand and slipped it in my sweatpants, so she had a good feel. (I noticed he was sporting a good bulge in his pants too.)
So, satisfied that I was probably the real deal, and we were all turned on, we headed to their place.
I was a little nervous how it was going to go down, but I needn't have worried. As soon as we got to their room, the two of them stripped me naked, and then got naked themselves.
Then I see her mouth going back and forth between two hard cocks. It was like a scene from a porn film. Then the two of us kissing while she worked our cocks.
Next, down to the main thing they wanted me for - he got on all fours, ass ready. I knelt behind him and she knelt right behind me, so she could watch over my shoulder. Then she reached round and took hold of my cock, lubed it up and guided it towards his ass as she pushed me forward. They wanted to make sure I fulfilled my end of the deal: my cock was GOING to go in his hole! (With pleasure..!) we had a great fuck as she watched. Occasionally she would feel under my shaft to feel it sliding in and out of his ass.
Then a little break. Next, he fucked her as she sucked me and we kissed over her.
More horny play. He sat on my cock and rode it for a while, then when he was done, she said: "I'd like a go on that!". Straddled me, and guided my cock inside her pussy. (Yeap.. me not knowing quite what to expect!) She was in control as she bounced up and down - and made a lot of noise! ("Uhhm... I think that's...good noise? Oh yes!)
So turns out I can do ass as well as pussy. Who knew?! Felt very different and...wet.. compared to an ass. The way it felt, lips gripping my cock as it pulled out, then easily took the whole length in again.
Then he starts to encourage her.. "Yes! Go on babe.. ride it...make him cum!"
Then she went for it... "Yes! Make him cum!" I'm pretty helpless underneath as she rides me. It's clear the pussy is a very efficient, purpose-built cum extraction device. It's not going to let my cock go until it has done the job it went inside there to do - deliver every last drop of cum. (And that it did, as the inevitable happens - I can't hold back as I feel it pulsating a load.. wow!)
A very hot and horny time. There were five holes available, and my cock went inside all of them..
(Anyway, hard and leaking a bit in my pants now thinking about it!)
Maybe one day I'll get another MMF opportunity. Not so easy to arrange...