The morning suit is the attire traditionally worn by the bridegroom. It is generally recommended for formal ceremonies that take place before 6:00 p.m. and where the bride is dressed in white, with a train and veil.
The accessories that must accompany a morning suit are a top hat and a walking stick, which should be left to one side during the ceremony itself. The suit must be worn with a white shirt with cufflinks and a stiff collar. A dress cravat is the classic choice, but a simple silk tie is also perfectly acceptable. A string tie or bow tie must never be worn. As for footwear, black lace-up shoes are essential.
With regard to the wedding guests, the rule is that if the groom is wearing morning dress, so must all the male guests, or at least the witnesses of both the bride and groom. These are of course traditions, not rules set in stone, and many grooms prefer not to impose their choice on guests.