Above is a picture of Polycarp being martyred. He is my favorite Church Father, I like how he knew the Apostle John in person, yet taught many years into the second century.
Studying the Church Fathers is important. The faith was once and for all delivered to the saints (Jude 1:3). That being the case, if someone is teaching a brand new doctrine that cannot be demonstrated in the writings of the Church fathers, then odds are it is probably heresy. Also, these are the saints of our heritage and we should study their works and learn from their struggles.
1. Church Fathers on Sola Scriptura
2. Church Fathers on Sola Fide
3. Church Fathers on Sola Gratia
4. Church Fathers on the Real Presence