One habit to change: Read your comp before you choose a style; with a brawl tank and plenty of healing, play frontline with the beam, otherwise take off-angles with orbs.
Good into
D.VaMatrix can't eat your beam: charge on her mech and keep the beam on.
DominaBeam her barrier for charge and ammo, then turn the beam on her.
GenjiDeflect can't stop your beam. Fight him with charge, ideally inside a turret room.
Struggles against
PharahSplash kills turrets and the teleporter from the air, and she puts your tank under pressure all game.
D.monRuns straight at you and either soaks your beam or leaves before it ramps.
Best maps
Best by win rate: Antarctic Peninsula, Lijiang Tower, Nepal and Samoa
Narrow, short maps, where the teleporter's 25m range is enough
Playing against Symmetra
Break her turrets before you engage. Without them she's squishy, slow and short-ranged.
The full guide is in the app
All 53 of Symmetra's matchups with a plan for each, map tips, comps, perks and kit. In a match, Hardstuck tells you when to stay on Symmetra and when to swap.