Now, all free icons from [Font
Awesome](https://fontawesome.com/icons?d=gallery&m=free) can be used on
odoo. It also adds three options in order to add the icons: \*
solid_icon \* regular_icon \* brand_icon The usage depends on the
configuration of the icon.

For example, brand_icon is necessary if we are using an icon of a brand:

    <button brand_icon="fa-amazon-pay" string=" fa-amazon-pay"/>

    <button brand_icon="fas fa-hand-sparkles" string=" fas fa-hand-sparkles"/>

    <button brand_icon="fas fa-handshake-slash" string=" fas fa-handshake-slash"/>