Did a real, physical dove appear at the Baptism of Jesus, or is this just metaphorical language (maybe a symbol found at various places in the Scriptures?)? Maybe someone could shed light on this.
There was no dove at the baptism of Jesus. Read the scripture a bit more closely and you see that:
Then John testified, “I saw the Spirit descending like a dove from heaven, and it remained on him."
It was the Holy Spirit which came down like a dove.
Just to add to Flimzy's excellent answer. There are several instances in the Bible where the Holy Spirit is seen in a physical form.
All Scripture is quoted from the King James translation, unless otherwise noted.
Once in the Old Testament he is seen as a hand writing on the wall.
Daniel 5:5 In the same hour came forth fingers of a man's hand, and wrote over against the candlestick upon the plaister of the wall of the king's palace: and the king saw the part of the hand that wrote.
Daniel 5:24 through 28 Then was the part of the hand sent from him; and this writing was written. And this is the writing that was written, MENE, MENE, TEKEL, UPHARSIN. This is the interpretation of the thing: MENE; God hath numbered thy kingdom, and finished it. TEKEL; Thou art weighed in the balances, and art found wanting. PERES; Thy kingdom is divided, and given to the Medes and Persians.
And also in the New Testament;
Acts 2:2 through 4 And suddenly there came a sound from heaven as of a rushing mighty wind, and it filled all the house where they were sitting. And there appeared unto them cloven tongues like as of fire, and it sat upon each of them. And they were all filled with the Holy Ghost, and began to speak with other tongues, as the Spirit gave them utterance.
With these and other Biblical accounts of the Holy Spirit appearing in a physical form it is not so strange or even mystical that John should have seen the Holy Spirit in some physical form descending on Jesus like a dove.
22 and the Holy Spirit descended upon Him in bodily form like a dove, and a voice came out of heaven, “You are My beloved Son, in You I am well-pleased.”
We can try not to analyse too much. It is physically a dove but also mythically or spiritually, the Spirit descending economically on the Lord for His ministry.