Credit: Larry Busacca/Getty Images

Katy Perry lit up the Metropolitan Museum Costume Institute gala Monday in NYC -- literally.

Sans fiance Russell Brand, the "Hot N Cold" singer, 25, stepped out in a glow-in-the-dark gown (LED lights were built into the dress from shoulder to hem).

"I love it! I think it's so much fun!" she told "I feel like I have to wear something to represent women who do their own thing and have spontaneity!"

How did she get her dress to light up?

"I have this thing in my bra!" she told Us with a laugh. "I don't know if that's a good place for it or not!"

She said wasn't worried about any wardrobe malfunctions. "I’ll be all right!" she told Us.

Despite her unique look for the night, she said there's still one star she'll never be able to beat in the style department.

"Gaga, of course!" she told Us. "I can't wait to see what she’s wearing because she's always one step ahead!"