The Seven Deadly Sins were formed of members Meliodas found one way or the other. The Sins are a special order of Holy Knights that supposedly tried to overthrow the kingdom of Liones but were thwarted in their attempts by the Holy Knights.
Meliodas is the captain of the Seven Deadly Sins, the Sin of Wrath, symbolized by a Dragon. He looks like a kid who runs a bar that travels on a Boar called "Boar Hat". Meliodas makes an initial appearance with a broken sword that later turns out to be part of a seal containing the demon clan.
Diane the Sin of Envy, symbolized by a serpant, is a 29 feet tall Giant. For some reason, she left her home and lives among the humans. She is discovered sleeping inside a forest and soon joins Meliodas and the Boar hat on a journey to liberate Liones.
The Sin of Greed, Ban is the 3rd member of the Seven Deadly Sins. He is the most playful and yet times the most distant member of the group. Ban seems to have a developed relationship with the serving pig at the bar and often calls him "master". He is also immortal dubbed "undead Ban".
Harelequin, also known as King is the Sin of Sloth symbolized with Grizzly. He is calm and at times, quiet, but when it comes to protecting his friends, King is the most ferocious opponent anyone can have. He is also the King of Fairies and is over 800 years old.
The Sin of Lust Gowther, symbolized with a Goat is telepathic of sorts. He can read memories alter them or play with people's minds. Despite his frail looks, he is quite strong, as he easily overpowered Threader with the heels of his shoe.
The Sin of Gluttony Merlin is the sixth member of the Seven Deadly Sins to be shown. She is shown to be a sorcerres, a witch, and one that overpowered the sorcerres of the Kingdom of Liones very easily.