Metagaming is broken into two halves. There’s the acceptable “suspend your disbelief” type of metagaming, where the entire table just sort of agrees that certain things (like a character being able to hike miles at a time while carrying 300 pounds of gear, just because they have a good Strength stat) is a perfectly normal thing. When people discuss metagaming, that’s usually not what they’re referring to.

When people discuss metagaming, they’re usually referring to when the player acts on knowledge that their character doesn’t have. For instance, maybe the player has already read/played the module before, so they know where all of the traps in a dungeon are. And maybe they take a route through the dungeon that conveniently avoids or bypasses every single trap. It’s one of those things that’s difficult for the DM to police, because delineating the difference between “the player got lucky/had a suspicion because of something I said when describing the room” vs “the player already knows what is going to happen” would require mind-reading. And notably, the only person who enjoys this type of metagaming is the metagamer. If the DM and the metagamer are the only ones who know the module, the metagamer is ruining a lot of the suspense and potential dramatic twists for the rest of the players at the table.

Wisdom governs a lot of “I want to find out something about the environment/this NPC” skills. Perception, Insight, Animal Handling, and Survival can all be used to notice things in different scenarios, (notice a trap, catch a lie, intuit an animal’s intentions, follow a trail in the wilderness, etc,) and all of them are governed by Wisdom. The only real exception is Investigation, which is governed by Intelligence. But Intelligence is mostly focused on “you remember this thing” skill checks, rather than “you notice this thing” skill checks.

As a result, Wisdom checks are often targets for metagaming. For instance, Perception allows you to detect things like traps or environmental details that would otherwise go unnoticed. Maybe a treasure chest has a false bottom, with extra loot hidden below it. The metagamer has already read the module and knows about the false bottom. And the metagamer will usually try to find ways to “force” certain results that they want, or will blatantly act on knowledge that their character wouldn’t have.

In the above “treasure chest with a secret compartment” example, maybe the metagamer (knowing there is loot under a false bottom) says they want to thoroughly search the chest. The DM calls for a Perception check as they rifle through the contents. The metagamer rolls, and the entire table can see that it is low. The metagamer knows they failed the Perception check. But they still want the loot at the bottom of the chest. So they say something like “when I don’t find anything worthwhile, I smash the chest in frustration.”

Now the DM is in a tricky spot. Do they reward the player and reveal that by smashing the chest, the player finds extra loot hidden in a secret compartment? Or do they try to punish the metagaming by saying that they find a bunch of smashed (now worthless) loot in what used to be a secret compartment? It’s a judgement call on the DM’s part, because the DM can’t read the player’s mind to know if they were trying to metagame.

For another example, maybe an NPC tells a lie. The metagamer asks if the NPC is lying. The DM calls for an Insight check. The metagamer sees the low roll, and the DM says the NPC seems to be telling the truth. Now the metagamer is in a spot where they (as the player) don’t believe the DM. But the metagamer’s character believes the lie, because they failed the Insight check. Now the metagamer may try to find ways to circumvent that failed Insight roll, by finding other ways to catch the NPC in a lie. Maybe they try to poke holes in the NPC’s story using History, Religion, Arcana, Nature, and/or Investigation (all governed by Intelligence) checks instead. Or maybe they go out of their way to find evidence that would disprove the lie. Even though their character would have no reason to do so, because their character believes the lie.

By hiding Wisdom checks from the players, it helps eliminate a lot of metagaming. Especially in the last example. If the Insight check was hidden from the player, the player wouldn’t know if they failed the check. So they just have to take the DMs word when they say the NPC seems to be telling the truth. It eliminates the entire “player saw the low roll and doesn’t believe the DM” part of things.

Bob: "Do I see anything?"

[Rolls a 1]

DM: "You see nothing"

Bob: "Well, DM probably only said that because of my shit roll, I bet there's something here"

Bob presumably has been using player knowledge to inform character decisions in a way the group doesn't like.

For example, illusions may require a wisdom check to realize they're not real. When Bob rolls openly on the table and gets a 1, he decides as a player that his character is going to treat the lava monsters as illusions. If he instead had to roll in the opaque jar, he as a player would be less certain about if they're illusions or real.

So first off, Meta-gaming in DnD is a bit weird. It's both acceptable and not acceptable, depending on the limitations therein. Like it is technically metagaming to have one PC trust another after just meeting in the game for the first time but this is not just acceptable but actively encouraged in some games because you don't want to draw out being untrustworthy of your party in the first session when the whole goal is to play together.

But the flipside is bad metagaming like if you read a module ahead of time, have information about that and then use that to take actions like fetching a bad guys bugout bag and investigating a specific wall to see through the illusion (Fuck you, you giant turtle asshole... sorry. Bad experience) then that is just you being shitty because you're not really playing the game. This is taken a step further with dice rolls. You may or may not notice that some DMs will ask for a specific DC and other ones will just ask for a roll and then tell you if you succeeded/failed after the fact. The ones who ask for it after the fact have typically dealt with a lot of Metagaming Bobs. People who, when they hear a specific DC, will roll just barely that DC or roll to beat it. Especially if it is a big and important roll. They don't want the dice to tell the story, they just want to win. They don't understand the game. To them it's being the hero or succeeding everytime so they'll lie about the dice rolls.

Metagaming bob is upset in this instance because the DM has elected to have all players roll in a specific thing so that only the DM can see the roll. That way only the DM knows whether they succeeded or failed. Bob feels like his agency has been taken away and he doesn't trust the DM. He thinks the DM will just lie about the rolls because Bob can't understand playing the game in any way other than how he sees it. He is mentally accusing the DM of doing what he does. So when he says that there is a problem, the DM knows that he has caught Bob.

From this point, Bob will typically flame out of the party. He will get upset about something and either be pushed out by all other players and the DM or just leave himself. Less often, Bob starts to learn the error of his ways and accepts the dice as the true storytellers and all of us just along for the ride.

I hope that helps and I hope that you have a fantastic session next weekend! May you always roll with advantage and the dice be forever in your favor <3