We get asked about this fairly often - you've made yourself a fine pure beeswax pillar candle (or some other wax I suppose), but you can't enjoy it because it's helplessly stuck in that metal pillar candle mold. I've been there. I've even pulled the wick right out of the candle trying to get the pillar out once. Don't do that.
I've got a few simple steps that work for us. But to start, you need a clean candle mold (if yours is dirty, get it clean!). Yeah, we sell those.
Now once you've got your raw beeswax (or whatever wax you've got in mind) fully melted and ready to pour (we recommend just barely melting your wax - high heat can easily damage beeswax), lightly but fully spray the inside of your aluminum mold with some natural cooking oil spray. We use some coconut oil spray from Trader Joe's, but any oil should do. It's important to do this right before you pour your wax as the oil will quickly slide down the sides and pool at the bottom if you diddle daddle too long.
That's my main big 'secret' step. You can also just buy some mold release spray for candles, but who knows what kind of crap they're made of, and if you're in to the whole natural thing, like us, oil should work. Now I just let the candle fully cool and set overnight, and come morning, I toss the whole thing into the freezer for 15 minutes and then once it's nice and cold I give it a good whack against the palm of my hand (or the kitchen counter, if need be) to jostle that candle loose, and then voila - you've got something too beautiful to burn.
You may have to stick the whole thing back in the freezer for another round of freeze and smack if it doesn't come out the first time.