Question, when a dm throws a flesh golem at us players and I as a wildfire druid know that the golems have fire aversion I cast a produce flame at it and hit. DM rules that due to it heavily raining it only takes half damage and then decides that it doesn't have the fire aversion and has advantage to saving throws instead of disadvantage along with no disadvantage on attack rolls. It just frustrates me when he has made it a mission to throw encounters at us that don't allow us to use any of our benefits(magical weapons, useful equipment, ect.) and has outright admitted that he is out to kill our characters. When brought up that this is a flesh golem and doesn't it have disadvantage on saving throws he called me out as a meta gamer. I wouldn't have asked if I didn't already now the type of monster that we were fighting. But seriously am I wrong to be frustrated?

Well, I'm of two minds about this.

As a DM, I enjoy homebrewing quite a lot, so I frequently will change around statblocks and take enjoyment from seeing how my table reacts to them; that and while I try not to be bothered by players having above-game knowledge about monsters (it's unavoidable, especially when it's a DM in the player seat), I will say it got REALLY irritating when a former player of mine kept trying to figure what monster I had used for that encounter.

That said: if a DM kept gimping my character for every encounter, and was doing so to actively try to "win" D&D?  I'd dump them super hard.

I wouldn't call this a "toxic DM" so much as a DM's "out to get the PCs" playstyle and loose consistency with rulings and your playstyle are incompatible.  The dynamic is problematic and calling it toxic is a bit melodramatic and seems to be done so to secure a moral victory in the anonymity of the internet.  It's fine to blow off steam here, I guess, but bro, does your DM DnD Beyond too, bro?

There is a playbook where the DM takes players outside of the character's comfort zone, usually some compromising of their presumed powers and advantages, to sort of rattle their mettle.  I'd say the DM, as you've described them, was trying for that but did so in a very sloppy and inconsistent way.  If they had a bit more forethought and follow through, I'd say the styles not for you.  But I'll admit the DM's preparedness seemed overconfident but unexamined at the start.  MIght not be used to being questioned.  Your rules grasp may be stronger and thus he found you a challenging player, and thus the metagaming accusation, what they really means is they felt you were using the rules to redirect the course of the game as the DM thinks it should be going.  It's a tough area to negotiate when this sort of conflict arises ... 

Best practices at tables usually entail a Session 0 where play styles and expectations and desires for the game are explained.  Seems that wasn't done or people talked past each other or weren't paying attention or weren't intending to be considerate of those intentions.  You're under no obligation to continue this game.  You don't need an allegation of toxicity as just cause for leaving.  You don't like the way they run the game, so you leave.  

Thanks guys, I appreciate the advise and I do agree with everything said. I did need to vent a little and get some outside feedback. Giving a little more context this is the first time I've played and while I have enjoyed the campaign and the people I'm playing with. I feel I'm not really vibbing with the out right admittance that the DM made that he is out to kill every character in the campaign.  Keep in mind this is not a homebrew campaign either. But I understand the fudging stats and making the prewritten encounters your own, however the constant undercutting an ability, the blatant targeting of specific players characters in game(party member is on his 5th character, two only lasting one session) and the distracted manner in which he conducts game play(we play online, since 3 members are out of state) I think I'm going to drop out. Which is sad to say because this was my first exposure to DnD.

Quote from Kasida >>

Thanks guys, I appreciate the advise and I do agree with everything said. I did need to vent a little and get some outside feedback. Giving a little more context this is the first time I've played and while I have enjoyed the campaign and the people I'm playing with. I feel I'm not really vibbing with the out right admittance that the DM made that he is out to kill every character in the campaign.  Keep in mind this is not a homebrew campaign either. But I understand the fudging stats and making the prewritten encounters your own, however the constant undercutting an ability, the blatant targeting of specific players characters in game(party member is on his 5th character, two only lasting one session) and the distracted manner in which he conducts game play(we play online, since 3 members are out of state) I think I'm going to drop out. Which is sad to say because this was my first exposure to DnD.

Probably for the best.  There's an argument to sit down with the guy and go "Look, from a PC standpoint it's hard for us to get to know our characters and really figure the game out when we're always rerolling new ones.  Can we cut it down a bit?" like MidnightPlat suggested, but if you decide to go that route don't forget your own personal shit too.  If they just flat out refuse to budge, then walk.  Someone will inevitably post the No D&D is better than Bad D&D schtick, but really it's more about people jiving first.  It's evident that isn't happening, and that's what comes first.

Quote from Kasida >>

Thanks guys, I appreciate the advise and I do agree with everything said. I did need to vent a little and get some outside feedback. Giving a little more context this is the first time I've played and while I have enjoyed the campaign and the people I'm playing with. I feel I'm not really vibbing with the out right admittance that the DM made that he is out to kill every character in the campaign.  Keep in mind this is not a homebrew campaign either. But I understand the fudging stats and making the prewritten encounters your own, however the constant undercutting an ability, the blatant targeting of specific players characters in game(party member is on his 5th character, two only lasting one session) and the distracted manner in which he conducts game play(we play online, since 3 members are out of state) I think I'm going to drop out. Which is sad to say because this was my first exposure to DnD.

Thanks for clearing that up, for a new player you certainly seemed to have a better grasp on the mechanics than most first timers.  Some DMs can "bully" other are just sadists (and there are compatible players some may consider masochists); but that's not your thing (and it's not really as common thing as way back in the day when players would line up at conventions to run through "meat grinder" dungeons).  

There's a saying "no D&D is better than bad or unfun D&D".  Your first exposure isn't an uncommon experience, but there's also better D&D, or D&D more to your liking.  Learning point / take away from the experience: there are very different sometimes conflicting styles of play out there and vetting a new table is always a good move.  If you're doing online play, before committing, if it's an active campaign ask if you can observe a session.  It's totally fine to say you had a bad first experience so you want to take a better look at the next game you're joining.  As a DM I'd be flattered/happy I had a prospective player that serious that they'd want to take a qualitative look at how I run my table.  As a first time new player you definitely want an "available" DM.  Someone who'll be willing to answer questions or show their game to you etc.  There's a sort of patience a good DM needs to, frankly, contain new player enthusiasm and integrate it into the tables campaign or existing dynamic.  It's not a necessarily uncommon skillset, but not every DM has it (contrary to what the internet tells you, it's a hobby, not a profession, so standards vary). 

On the positive note, you know the dynamic you were in just wasn't for you ... some players take a while to come to that conclusion so it's good to be able to articulate that you're not liking a situation and you know what a better situation would look like.  Those scenario's exist, it just takes some asking and "pre-gaming" to find them.  Good luck.  

Quote from Kasida >>

Question, when a dm throws a flesh golem at us players and I as a wildfire druid know that the golems have fire aversion I cast a produce flame at it and hit. DM rules that due to it heavily raining it only takes half damage and then decides that it doesn't have the fire aversion and has advantage to saving throws instead of disadvantage along with no disadvantage on attack rolls.

Regarding the rain, that seems fair. In future ask your Dungeon Master to establish rules on magical fire being extinguished by standard rain, as I've had conversations about flavouring Poison Spray and Acid Splash (the acid used in the latter not being the same as stomach acid, so it can't be flavoured as a gut grenade, for instance.)

Regarding the fact it doesn't suffer the adversive effects of fire, I'm fine with that as homebrew as other users say. Especially if this is a significant encounter, I could understand its typical weaknesses being changed. But the rest of this such as advantage to saving throws and no disadvantage on attack rolls seems overkill. That to me seems like the DM is out to get you. There's homebrew, and then there's taking the piss.

Quote from Kasida >>

It just frustrates me when he has made it a mission to throw encounters at us that don't allow us to use any of our benefits(magical weapons, useful equipment, ect.) and has outright admitted that he is out to kill our characters.

 If they've said that then yes, I would say they're a toxic DM. Unless this was explicitely stated during Session 0 that this is going to be heavily adversarial, The Apocalypse Stone levels of spite, then sure. But even then you can do that without deciding the way the player interfaces with the game - their character - is useless.

 For the sake of fairness I must say that we only know your side of the story. This "outright admitted" could be a joke, a misunderstanding or a complete fabrication. If you went into this game knowing full well the DM was in a killer mood, that's on you.

Quote from Kasida >>

When brought up that this is a flesh golem and doesn't it have disadvantage on saving throws he called me out as a meta gamer. I wouldn't have asked if I didn't already now the type of monster that we were fighting. But seriously am I wrong to be frustrated?

 It's only meta if your character wouldn't know that. Does your character know that the circumstances should have those results, and if yes, does it add to the atmosphere of the game when it doesn't work? I'm reminded of Pathfinder: Kingmaker where one of the key stories is trolls not having their signature weakness to fire, which the party discovers is due to a magical artefact. If that's the sort of reveal then fine, I'd be OK with that. I would not be OK with the DM pulling out advantages from their backside all of a sudden to try and kill me. If the DM wants to do that, they can play Iratus: Lord of the Dead and I can play with someone else.

If what you've said here is true and there's no omissions that would make your DM look more favourable then yes, I'd say you're right to be frustrated.

EDIT: Having read the entire thread, I think it's best that you exit that group (having explained that you don't mesh, preferably well in advance) but you've learnt quite quickly the golden rule of D&D: no D&D is better than bad D&D. I hope you find a group that's more fitting, and that this experience tells you to let people know what kind of game you want. At least you know now what kind of game you don't want.