How to change the player's model with code? [SOLVED]

So I'm trying to make a game where the players load in, there is a short period of time that passes, and then the game chooses one player at random and makes them the "monster". Please keep in mind that I'm a noob. Well, I have the model for the monster and know the code for everything else, but I don't know how to change the player's model to the monster model. I've searched online for a few days but I couldn't find a way to do it while the game is running. Any help? Please let me know if you don't understand the question and I can try to explain further.

Edit: I was able to figure it out by experimenting with some variations of the code suggested in the comments. Here is my code:

local monster = game.ReplicatedStorage.Monster

game.Players.CharacterAutoLoads = false

game.Players.PlayerAdded:Connect(function(player)
    print("Found Character")
    local monsterCharacter = monster:Clone()
    monsterCharacter.Parent = workspace
    monsterCharacter:MoveTo(Vector3.new(0,50,0))
    player.Character = monsterCharacter
end)

Now all I have to do is add animations to the character. Thanks to everybody that helped!