The blockbuster beauty put her acting skills to the test when she had to defeat robots that weren't physically there.
"It's always interesting, but (for) that one (a robot shown in the clip), we had a weighted sandbag that was a prop, the appropriate weight for the robot, and so I was actually holding it with those tools, whatever kind of tool that was, and fake wrestling with it," Fox told Early Show co-anchor Harry Smith.
Fox joked that she really isn't a motorcycle mechanic, like her character in the movie.
"I'm not. I can't even ride a motorcycle!" she admitted.
In some ways, Fox says, her life has changed since the first "Transformers" movie.
"The success of the first movie obviously opened a lot of doors for me, career-wise, that wouldn't be opened had I not been a part of that film," she said. "But my personal life, I mean, it hasn't changed that much. Like people take my picture a little more often. Other than that, it's still relatively the same. I don't ever leave my house. I'm a hermit."
Smith, who saw the "Transformers" sequel in IMAX, said there were people sitting on the floor waiting for the next showing. "It's more than just a movie. It's more than meets the eye," he said.
"You beat me to it!" Fox said. "I was going to say it. I was right there and you got it first!"
Although Fox admits she's usually reluctant to watch the films she stars in, she watched "Transformers: Revenge of the Fallen."
"I have seen it. I usually don't watch things that I do because I'm very neurotic about it and I can't sit through it, but I had to watch this because people were saying, 'Megan, it's really good. You have to watch it if you are going to promote it. It's massive.' I don't know how you saw it in IMAX without having a brain aneurysm or at least a migraine headache!" '
Smith sat in the second row in the IMAX Theater "and lived to tell about it," he joked.
He also admitted didn't understand it all and wondered if that was the case for everyone in the audience.
"I'm in the movie and I read the script and I watched the movie and I still didn't know what was happening," Fox joked. "So I think if you haven't read the script and you go and you see it and you understand it, you may be a genius. It's a movie for geniuses."
Millions of people who go to see it openly embrace it with applause and laughter.
"Apparently, people like it, which I'm excited about," Fox said.
Smith showed Fox a clip of his interview with Shia LaBeouf from Monday in whcih LaBeouf spoke about his co-star.
"It's like kissing a unicorn or something. How is this person real? She's phenomenally gorgeous and a really awesome person," LeBeouf said.
"Hmm," Fox said. "I think he was trying to say that he thinks I'm special. I think. I remind you of a unicorn, also? What about a Woodland nymph fairy?"