There are very few, if any, apps that do not employ some forms of icons and even if these are only launcher and, action icons, the correct choices and design make the difference between a successful UI and a confusing one.
Although it is not essential, Google is very keen that we use material design icons. This is an attempt to create a uniform user experience across the platform to counter the perception that iOS offers a more consistent feel. This is unsurprising, as iOS is a closed system that places a lot of restrictions on the developer. Google, on the other hand, prefers to offer a far more creative freedom to developers. In the past, this has led Apple devices to gain a reputation for being generally slicker than Android and, to counter this, Google introduced material design guidelines, which have gone on to far exceed original expectations and can now be...