How can I make a brick facing the player all the time?

For example, a game presented a big head with eyes, where ever the player move, the eyes will stair at the player. For like a security camera, it moves as the player moves.

Use the constructor CFrame.new (Vector3 position, Vector3 point) It makes an object point toward a given point which can be the nearest player. For example:

local pos1= game.Players.LocalPlayer.Character.Head
local pos2 = game.Workspace.Part1

pos1.CFrame = CFrame.new(pos1.Position,pos2.Position)

or --//game.Players.LocalPlayer.Character.Head.CFrame = CFrame.new(game.Players.LocalPlayer.Character.Head, game.Workspace.Part1.Position)

If you want a working script I will make it.

local part = Instance.new("Part",workspace); -- part for test
part.Anchored = true
part.CFrame = CFrame.new(0,10,0) -- sets part CFrame


local function getClosest(max) -- checks closest Humanoid and assumes it has a head.
	for i,v in pairs(workspace:GetChildren()) do
		if v:IsA("BasePart") and v:FindFirstChild("Humanoid") and v:FindFirstChild("Humanoid").Parent:FindFirstChild("Head") then
			dis = (part.Position - v.Position).magnitude
			if dis <= max then
				return v
			end
		end
		 
	end
end

spawn(function() 
while wait() do 
part.CFrame = CFrame.new(part.Position,getClosest(60).Position) -- makes part turn to person's head within 60 studs
end)