Melgar was killed in Mali at US Embassy housing he shared with several other special operations troops in the country.
The suspects include two elite Navy SEALs and two Marine Raiders. One of the accused is a member of the SEAL Team Six, famous for killing Osama bin Laden.
The Navy brought charges against the troops on Tuesday including felony murder, conspiracy, obstruction of justice, hazing and burglary.
The men allegedly drove to Marine quarters to acquire duct tape before breaking into Melgar's room while he was asleep, using the tape to restrain him and then strangling him in a chokehold. They killed Melgar "while perpetrating a burglary," the charge sheets say.