Unless you're absolutely intent on putting the pot outside and planting in it, it would be wise to consider the value of what looks to be a somewhat antique copper vessel. Drilling holes in it would not only reduce the value but also render the pot useless for any other purpose.
Instead, why not use the pot for an arrangement of dried or decorative type flowers and greenery... Being outside wouldn't necessarily hurt it but I believe your proposed plan to turn it into a "live plant" planter should be reconsidered unless the pot has no intrinsic value to you, either as a family heirloom or otherwise, other than just being a nice copper pot.
JMO
Steve

I agree with Steve, I would not change the appearance or character of that copper pot. I would not leave it outside either. It will weather and turn green.

Maybe you can use it as an indoor planter, placing another pot with its saucer inside.

Omar