A priest is a man who has received the Sacrament of Holy Orders.  Protestants have no concept of a Sacramental System.  Even those Protestants who have "Sacraments" they use the same word but mean very different things by the word.  For Protestants, Sacraments are no more than "Ordinances."  They do not cause and signify the graces of redemption as they do for Catholics.  

Because a priest has received the Sacrament of Holy Orders, he has been configured to Christ in a special way that enables him to celebrate the Sacraments, in particular the Eucharist.  He is called "Father" because through the reception of the Sacrament he relates to the people he serves in the manner of "Father."  The priest is their head and shepherd.

As I said, Protestants have no concept of this.  For them, there is no ontological difference between the minister and the congregants.  The minister just has a formal commission from the sect and a calling from a particular congregation.