William Dean Martin (aka Billy Martin), born June 15, 1981, is the guitarist and keyboardist for Good Charlotte. Billy has a website for all of his art called "Bloodzilla" and a clothing line, Level 27, and is currently sponsoring skateboarders since over a year ago, with his best friend, Steve Sievers. He is also currently working on a children's book called "Damious McDreary: A Boy And His Bat". He is a vegetarian and is active for PETA He is 6'2" His favorite foods include peanut butter and bean burittos His musical influences include Silverchair,Nine Inch Nails, Michael Jackson, Depeche Mode, Incubus, Deftones, and Korn His favorite movies are Nightmare Before Christmas and Who Framed Roger Rabbit? He plays Paul Reed Smith PRS guitars, Mesa Boogie Amps and BOSS effect pedals He designed a PRS called an PRS SE Billy Martin. He also plays a PRS Singlecut as in The Anthem, and Predictable music videos He played in a band called Overflow with friends Steven Sievers and J.D before joining Good Charlotte. Steve Sievers, a member of Overflow, is currently helping with LeVel 27. He is terrified of snakes. Billy is currently working on a children's book called "Damious McDreary: A Boy and His Bat".He also plans to do the illustrations in the book. This is said to come out in October. Lives in the San Fernando Valley area of Los Angeles Billy is engaged to his high school sweetheart, Linzi Williamson.

Tatoos:
Left upper arm:
- a toy-sodier
- a horseshoe
- a heart with a star
- 2 sparrows and a ribbon with "Mom"
- the Neon Ballroom-Cover-Logo from Silverchair
Left upper arm:
- a toy-sodier
- a horseshoe
- a heart with a star
- 2 sparrows and a ribbon with "Mom"
- the Neon Ballroom-Cover-Logo from Silverchair
Left elbow:
- star and clouds
- 2 cubes
- spider
- "GC"
Left forearm:
- 5 stars
- Jack Skellington skull and a spider web
- sunflower
Right forearm:
- Jack from "NBC", a cemetery, tombs and grinning pumpkins in the background
Left wrist:
- writing from "Lord of the Rings"
Left hand:
- a coffin inside of his middle finger
Right hand:
- a crown on his middle finger
Right leg:
- sword with "NFG" on it
- Kermit (on his knee)
Neck:
- "27"