Editor's note: Watch the full interview with Heidi Klum on Friday night. "Piers Morgan Tonight" airs weeknights on CNN at 9 ET.
(CNN) -- When R&B singer Seal and Heidi Klum met in a New York City hotel lobby, the supermodel told CNN's Piers Morgan, "it was kind of like two magnets."
The model-turned-mogul, TV superstar and mother of four is a guest on Friday's "Piers Morgan Tonight."
Klum said that she was sitting in the lobby with a mutual friend of hers and Seal's, and that Seal didn't even recognize the internationally famous model. Klum told the story of the couple's engagement, in which the singer had an igloo built on a mountaintop in the Canadian Rockies, to which he whisked her by helicopter.
"And then we get there," Klum said. "We hop off and the helicopter leaves, and there we are in the middle of nowhere. It was beautiful. And then he had his guitar with him. And he sang a song for me and he went down on his knee."
Klum described the igloo as "a full-on igloo with a bed inside with pillows and blankets and candles and rose petals."
When Morgan asked Klum how the couple manages to sustain such a happy relationship, Klum said "I just think because we love each other. We have fun with each other. We respect each other. I let him do his thing, even though that's hard for me sometimes."
Klum, 38, admitted that she had to forgo her propensity for controlling things and "learned how you have to, like, let him do his creative thing, because I am quite bossy in my industry."
When Morgan asked if the couple was planning on having more children, Klum answered, "No, we have four children, and we're complete now."
With the ninth-season finale of "Project Runway" coming up, Klum told Morgan she never imagined the series would last so long.
"No way," she said. "No. You just don't when you get into something like that. You know, when we first created 'Project Runway,' it was Harvey Weinstein, Desiree Gruber, my publicist for the last 15 years and myself, and we just shopped it around. We went to all these different networks and tried to explain to them what we wanted to do was a show about fashion."
Klum said that she had a hard time convincing networks that they had a hit for them.
"Everyone was like, 'Well, why is that interesting? Why would we want to watch how people make clothes?' " Klum said. When "Project Runway" finally found a network to call home, she said, what really led to success was word of mouth.
Klum told Morgan that audiences love the show "because it's really about talent."
When Morgan asked Klum if she grew up dreaming of being a model, the Germany native told the CNN host that as a child, she didn't even know that modeling was a career option.
"I didn't even know that that was a job, to be honest," she said. "I wanted to be a fashion designer."
Klum called her entrée into fashion modeling "pure luck" and likened it to "winning the lottery" when she told Morgan the story.
"I entered a competition," she said. "I, literally, out of a fashion magazine, cut out a coupon with my girlfriend, sent some random photos in that she took of me, entered this competition. And it went on for six months. It was a model search."
Klum, who also host's "Germany's Next Top Model" in her native country, told Morgan that she counts getting "Project Runway" on the air among her most cherished business successes. She also called designing her real passion and said she continues to design: There's a Heidi Klum for New Balance line of apparel and sneakers, Wildlife by Heidi Klum is sold on QVC, Heidi Klum on AOL, Shine by Heidi Klum, a fragrance with Coty, and more. Klum, who has lived in the United States since 1994, became an American citizen before the 2008 presidential election so she could vote for Barack Obama. She holds dual citizenship and remains a German.
"I've been paying quite a few taxes in this city -- in this country," she said. "And I felt that it would be right for me to vote for the next president."
Watch Piers Morgan Live weeknights 9 p.m. ET. For the latest from Piers Morgan click here.