Material-UI applications all share a common look and feel—to an extent. This doesn't mean that your banking application is going to look and feel the same as my music library application just because we're both using the same library. The common aspect is that both apps follow Material Design principles. I'm not going to go into depth on Material Design here, because there are ample resources out there that do a much better job than I could ever hope to do. Instead, I want to focus on the fact that Material-UI applications can be themed with a high degree of flexibility, and without the need to sacrifice the principles of Material Design.