Rachel McAdams Wows on the Red Carpet and Michael Sheen's Arm at Cannes

Rachel McAdams changed into a semi-sheer Marchesa gown for the premiere of her new Woody Allen movie during the Cannes Film Festival this evening. She and boyfriend Michael Sheen were also together this morning at the Midnight in Paris photocall, though they seemed to show even more PDA at tonight's event — Michael sweetly helped with her dress as she ascended the stairs, and they huddled close while posing alongside costars Owen Wilson, Adrien Brody, and the French actress Lea Seydoux. Rachel and Michael made the trip to France together in order to promote the comedy after a stay in LA doing press and hanging out with his 12-year-old daughter, Lily.