Commercials use the idea of self image in order to persuade their audience to buy a product. Commercials want to make you feel something when you see their product, they want to make you feel that you need their product in order to fit in your social groups, as well as to define the person that you are.
Commercials don't just sell a product, they sell your IMAGE.
Ethos is used in commercials to make an audience choose between what they believe is right or wrong based on their ethics. The way this is done is by representing an issue in politics, or a pressing modern argument, and presenting it in a way that it will cause people to agree with the company.