More about fallen angels, Satan was an angel but not as the name Satan or Lucifer or what 060606 had said
"Feriluce was Satan's name before HE fell from Heaven. Trust me."
Angels do not get names, only titles while they are in Heaven unless elected by and from the Serapheric Orders (undergod in way). Lucifer is just a position in heaven as the romans have called that angel in the latin name "light bearer". Its like in military form you would call someone a Sergeant or Petty Officer or the sort.
The angel who took the office of Lucifer was name Hylel meaning in Hebrew "Greatly Praised by God." the suffiex -el is in Hebrew of God.
Satanael - The adversary of God was entitled Satan for short, when he used the powers to convince Hylel to use his army, 1/3 of Heavens angels to wage war in Heaven so that Satanael can take over the Earth. Satanael did not possess an army. Only Gabriel, Hylel, and Michael were Generals of such armies.
As for Angels able to leave Heaven at will, that is not true. An Angel can not fall but not be a fallen. Fallen is deciding to go against God. After the Cherubim war (the fall of the Lucifer), God commanded all angels to make a choice then and there to be fallen or stay. After the decision was made those who chose to fall went to the Earth and married daughters of man to their chosing and lived human. The one who have defied God fell to Hades.

to me, this song is about a person who is aware that he doesn't fit in with society. he is aware of a different purpose for his life. i dated a dark angel for 4 years. he came into my life like the wind and fixed the darkness inside of me. because of him, i am a much stronger woman today.

"Powerless I watched from faces I'd assumed."

the faces he assumed are the roles he took on to fit in, but he yearns to find his place in the universe and be at peace. he feels that his purpose is to help others and "right the wrongs that [they] have suffered." and he feels this healing role is his purpose in which he can find peace.

"In your dream you see me clear
I have no restraint, no fear"

your conscious mind may not understand me, but your subconscious understands the truth about me. i am not a set label or defined role. i am my own person and i live without regard to limitations that most people live by.

"among my own i was alone through my own doing....it seems i came to leave"

he knows that he is not meant to commit to anyone but is destined to be in people's lives for short periods as a tool to help them grow mentally and spiritually. in short, he is a healer.

"Doubting angels fall to walk among the living."

angels that do not realize their purpose will not fulfill their destiny and won't live to their potential.

"Give me time I will be clear.
Given time you'll understand
What possesses me to right what you have suffered.
I'm in this mood because of scorn.
I'm in a mood for total war.
To the darkened skies once more and ever onward. "

you may not understand me now, but eventually you will realize my purpose. i am angry at how the world is and i am fighting to right the wrongs of others. my life's purpose will never end and i will always follow this path.

to me it is of someone reevaluating there life, not happy having lost himself along the way, so as he looks back seeing how he he tried to fit in do as others expected become someone and something other then what was at his core. so he goes back along the path that has led him to where he is looking for someone he used to be only to find it was not there any more, life had gone on and that is time for him to move on also.