Nay, not an angel at all, but an animal, even a dragon. Simply look at the first mention, Genesis 3:1 says plainly the serpent was more subtil than any beast of the field which the Lord God had made. Also see Revelation 12. You will never find one passage in the Bible that explicitly says Satan is an angel, but only that he masquerades as one.
He (Jesus) replied, "I saw Satan fall like lightning from heaven."
Was that a literal snake falling from heaven? Or are the demons
other angels that fell from heaven with Satan, himself a fallen angel?
"However, do not rejoice that the spirits submit to you, but rejoice that your names are written in heaven."
Those spirits, referring back to the aforementioned demons... are they also snakes? Why would He call snakes spirits?
the dragon and his angels fought back, but he was defeated, and there was no longer any place for them in heaven. And the great dragon was thrown down, that ancient serpent, who is called the devil and Satan, the deceiver of the whole world—he was thrown down to the earth, and his angels were thrown down with him.
A snake with a following of angels? Interesting...
From Job: And the LORD said unto Satan, Whence comest thou? Then Satan answered the LORD, and said, From going to and fro in the earth, and from walking up and down in it.
A walking, talking snake who is admitted to God's council and given permission to bedevil Job?