Frames and metatables

[Benalish]

If I have a frame, and the put a metatable on this all this methods, e.g. SetBackdropColor(), are overwritten. There's a solution to overcame this problem?

local frm = CreateFrame("Frame")
 
local mt = { __index =
    {
        foo = function() print("bar") end
    }
}
    
setmetatable(frm, mt)
 
frm:SetBackdropColor(0,0.5,1)

Error message: attempt to call method 'SetBackdropColor' (a nil value)