The meta right now has a lot of variety. With ou's resident bunnies finally banned, the tier is no longer as restrictive. As said by Dreepy, the best way to learn how to team build is by playing the meta and gaining an understanding of it yourself. The best thing that can be offered instead is to get a list of notable Pokemon in the tier that you should account for regardless of the type of team you are building
With the bunnies banned, Garchomp now reigns over the tier and for good reason. It no longer has to run that dumb tank set and is free to use its most dangerous offensive sets to its fins content. The most common set that you are gonna run into is sd scale shot, which is possibly the most dangerous setup sweeper in the game, only stopped by metal birds and Rillaboom. Any team that lacks those is in great danger of just being pried apart by Garchomp. Landorus Therian can somewhat slow down Garchomp but in a prolonged battle, Garchomp will kill Lando. Other sets include sd stealth rock which replaces scale shot, mixed set, tank sometimes even makes random appearances and more importantly, a very rare and a surprise choice scarf set can easily cause you to derail if not careful. Oh, and it still has sand veil as an option and that ability causes its enemies to go defcon one
With Garchomp reigning over the tier, Dragapult is a close second. It has already been a great offensive threat since ghost horse was banned but now, it can finally enjoy being the fastest mon in the tier. The most common sets are status hex, specs and dragon dance. The first two are easily dealt with by Blissey while dd set is more difficult. The biggest issue with Dragapult is, like Garchomp, you will not know what set it is running until it reveals itself because it can run whatever the hell it wants. An assumed specs set can suddenly be a dd set and now you're Blissey is dead. So, scouting is probably the safest option for this thing
Tornadus Therian is another mon which is a massive threat, mainly because its speed is ridiculous, has nasty plot and it can't even be worn down because of the very balanced boots and regenerator. While it is at the mercy of rngesus, that still doesn't mean it's not a threat. After a nasty plot, if it can actually aim, Tornadus Therian becomes a massive threat that very few mons can resist, such as only Tapu Koko. Even Slowking can't effectively wall it as it cannot kill Tornadus and green bird can simply go double nasty plot and brute force its way thru. Blissey and Tyranitar might be good counters, oops, focus blast. The thing about Tornadus is that it can also run a utility set, which I think is more annoying because it's the best knock off user in the tier but still, it is a massive threat
Rillaboom and Kartana. I'll group these two together because they basically play the same, except RIlla provides incredible speed control. Since they're grass types, their mortal enemy are birds, especially metal birds. With Rilla, band is a very common set since all it has to do is spam you turn, glide or knock off while Kartana usually has swords dance with life orb, turning it into a very powerful wall breaker, again, only truly stopped by metal birds. As such, Magnezone is a great partner for them as it deletes metal birds like nothing else
Tapu Lele and Kyurem. I'll also group these two together simply because they are a massive pain in the ass to switch into. Blissey might be a good choice, oops, specs psyshock / focus miss. It's really their specs set that makes them so dangerous as they excel at ripping balance teams apart. While specs is dangerous, it's not the only set they can run. Lele has other fun stuff like expert belt, scarf or even a rare calm mind while Kyurem has sub roost, dragon dance and even expert belt itself
While these are not just the only threats, these mons are so threatening that whenever you build a team, you have to keep them in mind, either by out offensing them or building like five defensive cores just to be safe. There are also stuff like Zeraora or Latios or weather teams but the above mons are so common that you have to account for them
For defensive threats, the most irritating of them all is Heatran. This mon is such a pain in the ass as it literally has no counters. At best, your team can force a one for one trade but the fact remains that its trademark magma taunt set is so annoying to deal with. Its checks like Garchomp or Dragapult do not want to take repeated magma storms, if they hit, while defensive mons that take magma storm are dead in the face of Heatran. The defensive mons would be lucky if they can force a one for one
Corviknight is the next best defensive mon, and for good reason. It thwarts Garchomp, walls Kartana and has you turn. These days, it usually runs specially defensive spread to answer Tapu Lele, which makes it somewhat vulnerable to the physical threats who can brute force their way with neutral hits. However, its still a powerful defensive pillar due to its great typing and you turn
Slowking is the last notable defensive mon as it was mostly passed over for Slowbro but now, its talents to somewhat thwart Tapu Lele is in higher demand and with the bunnies banned, offensive grasses got better and in turn, physical bulky waters got worse
Like earlier, those are not the only defensive options. You have a whole lot of them but those are what usually saw increase in usage due to the recent bans. The others are still options but have remained mostly the same
Other than those notable mentions, here are some random things that you can expect in gen eight ou
Landorus Therian is still everywhere. Being the equivalent of batman's utility belt for ou, you better believe this thing is still popular. It is a reliable stealth rock setter and probably the biggest irritation for many physical attackers
If you see a Pokemon that is weak to stealth rock, then ninety nine percent of the time they are gonna run boots
Always have a knock off sponge, a Pokemon that doesn't mind losing its item that much. The reason for this is that there is no more z crystals or mega stones to absorb it and say for example, your Cinderace losing its boots, that would be bad. You need to have a Pokemon to absorb knock off and to play around them carefully
Switch moves are more prevalent than ever, with the negative priority teleport now joining the fray. Walls with a switch move usually have minimum speed to outslow their opponents
Weather teams, especially sand, are still quite common but that will probably require its own answer in order to fully explain
As mentioned earlier, the best way to learn how to team build is to actually play the the tier and understanding it yourself. What I've written here is just a list of mons that you need to account for when you're just starting out. They are the most notable offensive and defensive threats and you need to be ready to face one of them in any given game
