He is 5,000 years old, the oldest Immortal alive. His birth date, birthplace and how he died for the first time are unknown.

He was also known as Adam Pierson, the Watcher who was assigned to find... Methos: "I'm in charge of finding myself, and I make sure it never happens", he used to say. He joined the secret organization in 1984 (nobody knew that he was an Immortal) and left it in 1997. His mentor was Donald Salzer.

He got married 68 times — never to an Immortal however, because, according to him, it would be too much of a commitment.

He is a nice guy, with great sense of humor and an extremely sharp mind, but he already played for the forces of darkness — by being part of the Four Horsemen (along with Kronos,Silas and Caspian), the most terrible Immortals that ever existed. They spread terror in the Bronze Age, killing, raping and destroying everything in their way, just for pleasure.

He majored in medicine in Heidelberg, Germany, in 1453.

He has been many things in life. One of his alias was "Benjamin Adams", or rather, "the good Dr. Adams", as he was known in the 19th century.

He claims he got to know Helen of Troy, Socrates, Caesar and Cleopatra; the English poets Lord Byron and PercyShelley along with his wife MaryShelley (author of The Modern Prometheus, best known as Frankenstein), were his friends and he rode with Butch Cassidy and Sundance Kid.

He introduced himself to Duncan MacLeod on March 6, 1995, with the line "mi casa es su casa". On the occasion, he told Duncan he hadn't faced another Immortal in 200 years. Besides Duncan, only Joe, Richie and Amanda know he is Methos, the oldest Immortal  alive — and Amanda seems to know Methos from earlier times.

As he believed he wouldn't beat Kalas, evil Immortal who was after the Quickening of the oldest Immortal alive, he urged MacLeod to behead him and take his Quickening, before Kalas did, which Duncan refused to do.

He keeps a journal almost since writing began*. It has a few entries on Duncan MacLeod.

*Sumerians invented writing in 3,300 BC

He fell in love with Joe's waitress Alexa Bond and had to watch his love die from cancer, after trying desperately to save her life by getting the Methuselah's Stone, a mystic talisman said to give eternal life and invulnerability to the wearer.

Duncan and Joe think he is an arrogant pain in the ass sometimes.

He loves beer.

He drives a Range Rover.

He uses the Sword of Ivanhoe, a rendition of the Sword of Richard the Lionheart.

Guilty? No way.  "I haven't felt guilt since the 11th Century."

However...  "I spent years losing my conscience only for him (Duncan) to go and find it again."

But so many regrets:
"One of a thousand regrets, MacLeod, one of a thousand regrets." (About Cassandra)

To start fresh, maybe it's a blessing. We all have things in our past we wish we hadn't done. I know I do.