By Level Up:
* Pikachu: Learns Flash at level 31.
* Eevee: Learns Flash at level 30.
* Vaporeon: Learns Flash at level 30.
* Jolteon: Learns Flash at level 30.
* Flareon: Learns Flash at level 30.
* Espeon: Learns Flash at level 30.
* Umbreon: Learns Flash at level 30.
* Leafeon: Learns Flash at level 30.
* Glaceon: Learns Flash at level 30.
* Sylveon: Learns Flash at level 30.
By TM:
* Any Pokémon can learn Flash by using TM25. This TM can be found in the following locations:
* The Game Corner in Goldenrod City
* The Battle Tower in Goldenrod City (after defeating the Elite Four)
* The Trainer's School in Goldenrod City (after defeating the Elite Four)
By Breeding:
* Any Pokémon that can learn Flash can pass it down to their offspring.
Note: Some Pokémon may learn Flash through other means, such as specific evolution methods or events. However, the above list covers the most common ways to teach Flash in SoulSilver.