What are the “Powers of the Age to Come”?
I assume that you are quoting from Hebrews 6:5. In context, he is talking about what happens to those who have become Christians but who later fall away. To describe those who have been saved, he talks about “those who have once been enlightened [a code word for those who have been baptized in the early church] who have tasted the heavenly gift, who have shared in the Holy Spirit, who have tasted the goodness of the word of God and the powers of the age to come.” The use of the word “enlightened” is probably a reference to baptism, the heavenly gift is probably a reference to baptism, the next phrase is a reference to receiving the gift of the Holy Spirit (Acts 2:38-38). The powers of the age to come is probably a reference to heaven. There is a sense in which Christians are in the Kingdom of God, but we do not fully experience the Kingdom before we enter the New Heaven and New Earth–until after the final resurrection. So, I assume that he is referring to the Christian experiencing a taste of heaven in the Kingdom of God while still here on the earth as a Christian.