Solid Snake

Solid Snake, also known as Metal Gear, is a Steelix in AJ's party. He was caught in Victory Road as an Onix as the team was preparing to face the Johto Elite Four. Solid Snake eventually evolved after the Hivemind gave it a rare candy in Democracy, and notably defeated Zapdos multiple times at Mt. Silver, some of which were accomplished using only struggles.

History
Solid Snake was originally an Onix caught during AJ's run through Victory Road. Although mostly useless as an Onix, he became critical to the team after evolving into Steelix. The Mob's strategy to defeat Red was to give Steelix Leftovers, and then grind until he was able to take down AA-J leaving LazorGator open to taking down the rest of Red's team.

Personality (Lore)
Solid Snake was often portrayed as a gruff character, and sometimes is viewed as a loner. In one interpretation, Snake joined the party on Victory Road after having to be convinced of the merits of the journey that the team was on. Because they were caught around the same time, some art depicts Ace the Raticate riding on Snake's head, and places them as very good friends.

Although his later addition to the party in Generation 2 inhibited much lore to be developed about him, his contributions in the caves of Mt. Silver and against AA-j in the final battle cemented his legacy. Despite questions about his personality, it is widely agreed that Snake was one of the strongest of the Generation 2 final team, a workhorse of the team and one who was willing to carry the team when needed.

Name
Solid Snake (and his nicknames) are derived from the Metal Gear Solid franchise. Because of this, he is commonly depicted with a dark green headband and an eyepatch.

Trivia

 * Although caught late in the game, he ended up being level 73 by the end of the stream, making him AJ's second strongest Pokemon. This was in part due to him being in the first slot while climbing Mt. Silver, as well as being the holder of the Exp Share at one point.
 * He is the subject of the song "Metal Gear Steelix" by Church of the Helix Choir.