Metwally was born in 1974 in Queens, New York to an Egyptian father and a Dutch mother, and moved with the family to Orange County, California at age three, where he was raised. Metwally earned a BA in History from the University of California, Berkeley, and while acting around the Bay Area earned a Master of Fine Arts in Acting from the American Conservatory Theater, San Francisco.

Metwally's film roles include Non-Stop, Gavin Hood's Rendition and Steven Spielberg's Munich, Complete Unknown, Breakable You,The City of Your Final Destination, released in 2010 (filmed 2006–07), and Amsterdam. He received the 2008 Chopard Trophy for his work in Rendition, presented at the Cannes Film Festival. Metwally was also seen in the film Miral from Director Julian Schnabel.

Metwally has also worked extensively on stage, appearing in the world premiere of Rajiv Joseph's "Guards at the Taj" at the Atlantic Theater in 2015 where he also received an Obie Award for Outstanding Performance. He was seen in 2005 as "Aram" in Beast on the Moon directed by Larry Moss, and received a 2004 Tony Award nomination for his work in Sixteen Wounded. He has worked with the New York Arab-American Comedy Festival, first as an actor and then as a Director. He has also appeared at theaters around the country, including Steppenwolf, The Public, the Long Wharf, Berkeley Rep, and many others.