What Is Meta?
Meta or 'Most Effective Tactic Available' is quite literally the most effective team composition, Hero choice or strategy that fits the current patch. It will feature a select bunch of heroes that are currently strong, across the rank system, whether this be independently or with other heroes. Meta changes often as, usually, with each new season there is a new patch.
How Will I Know What To Pick?
As said previously you can usually tell with the patchnotes who will be effective or not as some heroes will receive buffs and nerfs every season. If you can't decide for yourself which heroes will be strongest you can check higher ranked players streams, Youtube videos, Overwatch League team picks or even websites that show hero selection statistics.
What If I Can't Play These Heroes?
Try not to worry about this; if you already know how to play the hero great, if you main them even better, but if you can't play them there is always leniency towards these types of situations. You most likely wont be in an enivronment, unless you play scrims or high level Overwatch, where you play meta anyway. Usually you see that ranks lower than Grandmaster wont play a whole team of meta picks, at most 3 heroes that are meta will be played at a time. In Overwatch 1 it was more common to play full meta team compositions, but it's not seen as much anymore in Overwatch 2. So, relax! You can always play a hero you're more comfortable on.
Team Compositions and Meta
Now onto what you've been waiting for!
Brawl: Brawl is probably the most common meta play and a lot of people play it without realising. It is essentially a team comp that can effectively steamroll an enemy with brute force and speed. It usually consists of:Tank: Reinhardt, Orisa, Sigma, Junker Queen, Rammatra DPS: Sojourn, Reaper, Soldier 76, Cassidy Support: Lucio, Kiriko, Brigitte, Ana
Dive: A team composition with high mobility that can easily overwhelm the enemy team, a lot of the characters are 'flankers'. It usually consists of: Tank: Wrecking Ball, Winston, D.Va DPS: Genji, Tracer Support: Lucio, Kiriko, Brig, Zen (for discord)
Poke: This comp sits as far away as possible - the aim is to basically kill the enemy before they reach you or before fights start. Usually consists of: Tank: Sigma DPS: Hanzo, Widow, Ashe Support: Zen, Ana
Rush: Take the enemy out as quickly as possible, this is like a mix between dive and brawl. It consists of: Tank: Reinhardt DPS: Mei, Reaper Support: Bap, Moira, Kiriko
Some common heroes you'll see together:
Reinhardt + Ana,
Pharah + Mercy,
Genji + Ana,
Widowmaker + Hanzo,
Echo + Pharah,
Tracer + Genji,
Ashe + Cassidy,
Doomfist + Kiriko