Honestly. Your mom told you it was taboo. Fashion designers told you that it should not be done.
Look, you can absolutely mix metals within your decor. Here are a few helpful tips to keep in mind!
Mix your metals outside of their own colour group. What do I mean? Don't mix chrome with brushed nickel as it will just look like you've made an oversight as the tones of the metals are the same, but the finishes are definitely different. Mixing brushed nickel with brass and a dash of rose gold? Yes please.
Pick one metal and finish as your main focus. Let that be your overall theme for your metals, but accent with small dashes of complementary colours.
Mix your metals with what you're doing decor-wise. Do you have a beautiful antique oak sideboard that has a honey tone? Use pops of antiqued brass and gold in the room, and throw in some beautiful large statement candlesticks that are made of polished silver. The tones will accentuate each other and really help make everything pop.
Obviously you know what you like, and what works best in your space. I'm just here to encourage you to try new things. Mixing metals isn't something that will get you thrown into design prison. It's a great way to show off your vintage and curated goodies together.