Yes, he really does exists and I will tell you the reason why. Satan who we refer to as supplanter or the devil, is an angel of light that was cast out of heaven and attained the status of the name satan because of his nefarious activities after he was cast out of heaven. The person who we now referred to as satan used to be called lucifer and according to the bible he was the fairest of all the angels possessing the gift to sing but according to the bible he grew proud and pompous of his talent, and as time went on he actually coveted the throne of God who was his creator and his God, and he desired to be worshipped (mind you this happened before Adam and Eve were even created and that satan was already casted from heaven before the creation of man).
So the devil who was called lucifer decided to rebel and he actually gathered some angels with him and then fought against the Lord's army which was actually led by the archangel michael it was a very tough war but god's angels became the couriers and as a result of this lucifer who we now call satan was cast out of heaven, and he decided to trouble the creation of god and became a menace to humanity as a result of his misguided perceptions about god he felt angry as to why he was cast out and and this rebellion brought about the wickedness and cruelty that we all now see from him.
Although we cannot be proven physically because he is not visible to the eyes and that's a result of lack of substantial evidence science has actually ruled his existence to be a ruse or so yes according to religion he is actually existent and the deep studying into the words of God we actually review, we can already see some of the dastardly activities brought by him all over the world and that is even the primary evidence of his existence
For me, "satan" is everything you are limited by, frightened/sad about, disappointed of, etc... That might be even simple things, like a pile of dust on your desk, which bothers you every time you are switching on your computer.
We can think about our live as a process of improving, structurizing, ordering, fixing things - otherwise it sometimes lead to a disappointment, sadness or even a disaster. We want to have a control of our life. We want to utilise long term, as well as minor "satan".
Adam & Eva were not aware of such problems until they fall behind the very first satan in their life - a snake's temptation.
Not sure whether I went to deep with my thoughts...
And here come the regurgitated BELIEFS...