Silver first appears in the Generation II games, lurking outside of Professor Elm's lab. During the player's journey to Mr. Pokémon's house, Silver makes his move, stealing one of Elm's two remaining starter Pokémon (coincidentally always the one that is strong against the player's choice). He will meet with the player on the outskirts of Cherrygrove City, battling to get through.
Silver shows a strong dislike of Team Rocket. He considers them to be weak, and vows to take them, as well as any other weak Trainer, down. He steals a Sneasel from a Trainer in Cianwood City and, while Ethan/Kris/Lyra attempts to take down Team Rocket in Mahogany Town and Goldenrod City, interferes to prove himself. It is in the Mahogany hideout that he meets with Lance, Champion of the Elite Four at the Indigo Plateau. Silver challenges Lance and is easily defeated by the dragon trainer, who then proceeds to berate Silver for his callous ways towards training Pokémon. Though Silver is outraged for losing to someone with such an attitude, the loss and Lance's words ultimately set him on the path to becoming a better person. When Team Rocket takes over the Goldenrod Radio Tower, Silver follows the player as they battle Team Rocket, hoping that Lance will reappear and he can request a rematch.
By the time the player reaches the Indigo Plateau, Silver battles against the player not out of malice, but to prove that he is a good Trainer. He is defeated and departs to continue training. The player battles Silver on Mt. Moon, and though he loses he claims he can feel his Pokémon getting stronger, and resolves to train at Dragon's Den. When battled the seventh time at Indigo Plateau, Silver seems to have finally learned to care for his Pokémon properly, as his Golbat has evolved to Crobat, which only occurs when Golbat is very happy. This is further expressed in Generation IV when his starter Pokémon starts to follow him around, much like the player's Pokémon; Professor Elm even expressly states that Silver's Pokémon have come to trust him when Silver returns to the lab, presumably to return the starter he stole.
Following Silver's final encounter with the player and after the player has become Champion, Silver can be found training on Tuesday and Thursday in the Dragon's Den, and will appear at the Indigo Plateau on Monday and Wednesday to challenge the player, should he or she appear. He does not appear at all on the weekends, indicating that he may in fact take the day off, resting his Pokémon. In Pokémon HeartGold and SoulSilver, Lance and Clair will sometimes appear in the Dragon's Den and challenge the player and Silver to a tag battle.
In terms of personality, Silver is the darkest of the rivals in the series. While most other rivals are generally good-natured, or at least zestful enough to crack a joke at the player, Silver is (at first) cruel, hateful, power-obsessed and even physically abusive, pushing the player character around several times. Even after he starts to become kinder, he remains a rather serious individual. He does, however, express genuine happiness when Elm allows him to keep the Pokémon he stole.
Giovanni and Silver's relationship is revealed in HeartGold and SoulSilver if the player brings a promotional Celebi to the shrine in Ilex Forest. Celebi takes the player back in time three years to witness Giovanni abandoning Silver to go into seclusion because of his defeat at the hands of Red/Leaf. Silver's hate for Team Rocket apparently stems from them failing his father.
Pokémon
The starter Pokémon that Silver has will depend on which Pokémon the player chose to bring on Professor Elm's errand at the beginning of the game. As with all rivals, it will be the Pokémon whose type weakens that of the player's starter.
