Lively, 26, looked gorgeous in a silk Gucci gown in blush, which was custom-designed for the actress and Gucci Premiere spokesperson, while Reynolds, 37, wore a taylor-made blue-velvet tuxedo.
The couple was all smiles as they wrapped their arms around around each other while walking the event's red carpet.
After costarring in the 2011 action flick Green Lantern Lively and Reynolds tied the knot in a private ceremony in 2012.
Monday night's Met Ball was organized by the museum and Vogue Editor in Chief Anna Wintour. The event was meant to honor British-born designer Charles James and the theme was "White Tie and Decorations."