If you are standing in a line when polls close, they are legally required to still let you vote. Do not believe anyone who says that voting has been extended to Wednesday; this does not happen.
Be safe, be smart, and if you see any attempts to block citizens from casting a ballot, be it intimidation, the requesting of specific pieces of ID, or anything else, contact the Election Protection Hotline (866-OUR-VOTE), the Department of Justice Voting Rights Hotline (800-253-3931), or any local officials such as your county clerk, elections commissioner, elections supervisor, or your state board of elections.