In Islam, Satan himself is a demon (jinn).
The demons can be bad or good, believers or not.
It's not symbolic at all as you can see in the different following verses.
God created them like us just to be believers :
51.56 And I did not create the jinn and mankind except to worship Me.
They will be judged as us in the Day of Resurrection :
6.130 "O company of jinn and mankind, did there not come to you messengers from among you, relating to you My verses and warning you of the meeting of this Day of yours?"
They can see us but we can't see them :
7.27 O children of Adam, let not Satan tempt you as he removed your parents from Paradise, stripping them of their clothing to show them their private parts. Indeed, he sees you, he and his tribe, from where you do not see them.
They are also aware of the previous Scriptures :
46.29 And [mention, O Muhammad], when We directed to you a few of the jinn, listening to the Qur'an. And when they attended it, they said, "Listen quietly." And when it was concluded, they went back to their people as warners.
46.30 They said, "O our people, indeed we have heard a [recited] Book revealed after Moses confirming what was before it which guides to the truth and to a straight path.
Some believed God had a son (maybe Jesus) and that Satan exagerated (lied):
72.4 And [it teaches] that exalted is the nobleness of our Lord; He has not taken a wife or a son
72.5 And that our foolish one* has been saying about Allah an excessive transgression.
* Satan, their chief
Some of them are good and others are bad :
72.10 And we do not know [therefore] whether evil is intended for those on earth or whether their Lord intends for them a right course.
72.11 And among us are the righteous, and among us are [others] not so; we were [of] divided ways.
72.14 And among us are Muslims [in submission to Allah ], and among us are the unjust.
Some worked/work for humans like Solomon :
34.12 And among the jinn were those who worked for him by the permission of his Lord.
34.14 And when We decreed for Solomon death, nothing indicated to the jinn his death except a creature of the earth eating his staff. But when he fell, it became clear to the jinn that if they had known the unseen*, they would not have remained in humiliating punishment.
*In Islam the djinns help the soothsayers to know some things about the humans.