Happening up in the D.C. region on Friday and this weekend:

Gay marriage: The U.S. Supreme Court today is expected to consider whether it will hear cases related to same-sex marriage, including a case involving the Defense of Marriage Act.

Handel’s “Messiah”: The Washington National Cathedral Choir will perform the holiday classic tonight at 8 p.m., with additional performances Saturday and Sunday at 4 p.m.

Metro delays: Metro plans to close the Takoma, Silver Spring, Forest Glen, Wheaton and Glenmont stations for weekend work, starting at 10 p.m. and continuing through Sunday.

U-Va. student memorial service: A memorial service will be held Saturday for University of Virginia student Casey Schulman, who was killed last weekend in a boating accident while snorkeling off the Caribbean.