A tie bar is functional.
It allows you to clip part of your tie to your shirt so that when you do bend down to reach for things or are walking in a strong wind it doesn’t end up in your face. The fact it can be a great little detail and stylish item.
The width of your tie will determine the size of you tie bar. The color of the tie bar may also determine the color suit you’d wear it with. But ultimately the tie bar should be worn with confidence… and always with your tie.