You need metatables for rolling your own OO system. But, object orientation (particularly when, as in Lua, you need to roll your own) should not be part of a be

You need metatables for rolling your own OO system. But, object orientation (particularly when, as in Lua, you need to roll your own) should not be part of a beginner curriculum. Like I said, by the time you need to worry about metatables, you should have already moved on to your second and third languages -- you can learn about OO in the context of Python or JavaScript and then later apply that to Lua.