When it comes to holiday parties, famed fashion consultant and "Project Runway" host Tim Gunn says it's important to dress up and have fun.

"Especially now, it's time to realize what the holidays are all about," he told "GMA."

Gunn -- who spoke to "GMA" as a Command Brand style adviser to help people incorporate their holiday fashion trends into their home décor -- said that he only recently learned that between Nov. 15 and Jan. 1, there are more than 20 religious holidays.

"We need some inspiration and some grounding, need to honor our values a bit," he said.

So, when it comes to hosting a party or attending that yearly office bash, don't wear what you normally do every day. Gunn, himself, likes to jazz things up a bit, and loves to pair a black velvet blazer with a tuxedo shirt, and a bow-tie. He keeps the look grounded by pairing it with denim.

"You're not taking yourself too seriously, but saying, 'It's the holidays and I want to be a part of that,'" he said.

While choosing a statement piece like the blazer is high on his list of holiday party do's, one thing he really doesn't recommend is hosting a party without keeping an appropriate outfit in mind. Sweats, he said, are a real mood-killer.

"I would dress up!" he said. "For me it's a sign you care."

As for any trends he's seeing that people can jump on, Gunn is all about metals like silver, gold, and copper and more, especially for accessories. As for clothing? Try tartan, he said.

"It's a classic, but on trend, at least on the runway," he said.

But most importantly, Gunn recommends having fun with fashion, and not taking it too seriously. If your office is hosting an ugly sweatshirt party, go ahead and dress for the occasion, he said.

"I think they are great! I had a mother and sister who have a whole collection of horrible sweaters," he said, laughing. "If you acknowledged it's really obnoxious and kitschy [you're on the right track]; if you think it's serious, you have a problem."