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 Gold/Kris/Kotone 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, who sets him straight about his callous attitude towards Pokémon, and ultimately causes him to start changing into a better person. By the time the player reaches the Indigo Plateau themselves, Silver battles against the player not out of malice, but to prove that he is a good Trainer. He uses a Crobat during this battle, illustrating that he finally considers his Pokémon to be partners and friends rather than tools, as a Crobat can only be obtained if it loves its trainer. 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, assumedly 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. And even after he starts to become kinder, he remains a rather serious individual, though he shows genuine happiness when Elm allows him to keep his stolen Pokémon.
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.
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.
As a possible reference to Silver's training schedule, Template:Ga also can be battled again (on Saturdays and Sundays) after the player becomes champion. He can also be found training at Stark Mountain during the week in Template:Game.
If Silver's stolen starter is Template:P, he uses Template:P at level 16 in his second battle, despite Totodile only being able to evolve from level 18 onwards. This error is corrected in Generation IV, though he still uses Croconaw, due to his stolen starter being Level 18 in Generation IV.
Additionally, if Silver's stolen starter is Template:P, he uses Template:P at level 32 in his fourth battle (level 34 in Generation IV), while the other two are their final forms (which is normal).
In his anime cameo, his only known Pokémon is a Template:P. All other game rivals that have made anime appearances have been seen with the Template:Type2 starter from their home region, indicating another possible Pokémon for Silver to have (which would also fit in weakening Jimmy's Typhlosion).
Two of Silver's Pokémon in his final team received evolutions in Generation IV. The same two Pokémon are also the only members of his team that did not evolve twice.
Perhaps coincidentally, neither of these Pokémon's new evolutions are available in HeartGold and SoulSilver until after the National Dex is obtained, as their evolution methods require certain forces external to the Pokémon (rather than knowing a move, as the five new Johto Dex additions do).