What it does
Solar Beam is a Grass-type Special move. Standard: charge on turn 1, fire on turn 2. Under sunny weather (from Drought or Sunny Day), the charge turn is skipped entirely — you fire the same turn you select it.
In rain, sandstorm, or hail: power is halved. In sun: full power, no delay. That combination is why sun teams run it.
The single-turn execution is everything in doubles. A two-turn move in doubles is almost always unplayable — you spend one action doing nothing while your opponent attacks freely, and there's no guarantee the target sits still. Sunny weather collapses that two-turn cost into one, making it play identically to any other attacking move.
A couple of mechanical edges: it can hit Pokémon in the Fly or Bounce semi-invulnerable state, and Sleep Talk cannot select it. Neither of those comes up constantly, but they're real.
Who runs it
Charizard (63%) is the highest-usage carrier in Champions. Fire/Flying covers a lot, but water and rock are both weaknesses — Solar Beam handles those exact types in one slot. In sun, it fires without delay, and Charizard has the Special Attack to back it up.
Torkoal (17%) carries Drought itself, meaning every time it switches in, the sun activates and Solar Beam can immediately fire with no charge. Its Special Attack isn't extreme, but as a weather setter that also holds a coverage threat, it's worthwhile.
Venusaur (13%) pairs Solar Beam with Chlorophyll (Speed doubles in sun), turning into a fast, hard-hitting special attacker the moment sun is up. Its Grass STAB means Solar Beam is operating at full STAB value.
Ninetales (22%) manually builds sun with Sunny Day and carries Solar Beam to cover Water and Rock matchups. Doubles as both weather setter and coverage attacker.
Typhlosion (21%), Castform (24%), and Scovillain (13%) each serve different roles within sun cores, using the weather condition to make the move work.
How to use it
Whether Solar Beam is usable depends entirely on whether sun is up. Weather setup paths: a Drought Pokémon switches in and triggers it automatically; Sunny Day is used manually; or in Champions, some specific mechanics. No sun means no instant-fire Solar Beam.
If the sun gets overwritten — rain, sand, or hail replaces it — Solar Beam immediately becomes a two-turn move at half power. Against rain teams, their weather actively destroys your plan. Factor this in when building.
Standard doubles flow: turn 1, your Drought setter like Torkoal or Ninetales switches in to establish sun; your partner like Charizard fires Solar Beam immediately on the same turn. If your opponent can't retaliate with a weather override right away, that's a high-power hit landing for free.
Decision point each turn: shield the support or attack? Sometimes letting your support Protect while the attacker fires Solar Beam is the right call. Sometimes you need to cover a threat first. Read what your opponent has active.
Tips & strategy
Sun is the lifeline of this move. Without it, Solar Beam is close to unplayable competitively — the charge turn is a free attack for your opponent, and the halved power in adverse weather makes it even worse. When building a sun team, the reliability of your sun setup comes before everything else.
When you see Drizzle or Rain Dance on the opponent's side, plan around the weather war. If they flip the weather, your Solar Beam goes from a nuke to a liability. Either have non-weather-dependent damage options ready, or have a way to re-establish sun.
Power Herb can fire Solar Beam without sun in standard play, but in Champions the item slot is usually contested — Choice Scarf, mega stones, and other held items often take priority. Sustainable sun setup is the more reliable route.