Satan is an Angel

 Ramban (|Iyov introduction) The book of Job mentions Satan. It is known from tradition that he is an angel who was created to oppose and harm Man as is implied by the word Satan. Our Sages say that Satan is also the Angel of Death as well as being the Evil \Inclination and he is also actually an angel and not a natural phenomenom. .He is also the basis of the stars of destruction and blood of wars and wounds and strive, He is part of the cycle of Mars and our Sages have said he is in the portion of Esav since he is associated with the sword and war. His portion also incudes the harmful demons (mazikim) and they are also called Se’irim. Esav and his people are Se’ir . The Angel of death  means he takes the soul which is the spiritual part of the person and must be done by an angel… The yetzer harah  is the spiritual aspect  that has desires and is similar to the mazel of fire and serves as the power to energize taking or lusting like a burning fire. In general everything G-d does in the material world is through an angel. Therefore since G-d wished to test |Iyov he authorized Satan to do it