A metatable in Lua defines various extraneous behaviors for a table when indexed, modified, interacted with, etc. They are Lua's core metaprogramming feature; most well known for being useful to emulate classes much like an OOP language.
Any table (and userdata) may be assigned a metatable. You can define a metatable for a table as such:
-- Our sample table
local tab = {}
-- Our metatable
local metatable = {
-- This table is then what holds the metamethods or metafields
