Since we are living in a postmodern day and age wherein virtually every single industry that currently exists in the world has been saturated to the point where obtaining a market share is only possible if you stand out more than anyone else is capable of competing with, the only pursuit that would make sense to you would be to make your business cards look extremely unique. In spite of the fact that this is the case, you should bear in mind that we have reached a saturation point when it comes to uniqueness as well.
It is important to note that since every business is trying to make Metal Business Kards that are extremely different from anything else that people might have seen, variations in design are no longer going to give you the same kinds of benefits that they used to previously at the end of the day. Business cards are meant to convey some type of information to anyone and everyone that you end up giving them to, which means that making them a little too fancy in their designs would be something that would do a lot more harm than good.
Sometimes a business card just needs to be a business card, and there is no real need for anything overly fancy. In fact, making a business card that is far too fancy might just have the opposite effect from what you were initially intending. It would distract people from the information that they are actually supposed to pay attention to which would go against your reasons for making them in the first place. Go for a simple design, something that would be effective yet basic.