Are the Sacraments symbols only?
No. They are means of grace by which God works invisibly in us, quickening, strengthening and confirming our faith in him.
Catechism for the Global Methodist Church, question 39
53Therefore Jesus said to them, "Truly, truly, I say to you, unless you eat the flesh of the Son of Man and drink his blood, you have no life in yourselves." 54The one eating my flesh and drinking my blood has eternal life, and I will raise him up on the last day. 55For my flesh is true food, and my blood is true drink. 56The one eating my flesh and drinking my blood remains in me, and I in him. 57Just as the living father sent me and I live through the father, so the one eating me will also live through me. 58This is the bread that came down out from heaven, not just as the fathers ate and died; the one eating this bread will live toward the age.
3Or do you not know that all of us who were baptized into Christ Jesus were baptized into his death? 4Therefore we were buried with him through baptism into death, so that just as Christ was raised from the dead through the glory of the Father, we too might walk in newness of life.
15I speak as to sensible people; you yourselves judge what I assert. 16The cup of blessing that we bless, is it not a participation in the blood of Christ? The bread that we break, is it not a participation in the body of Christ? 17Because there is one bread, we who are many are one body, for we all partake of the one bread.
12Having been buried with him in baptism, in which you were also raised with him through faith in the working of God who raised him from the dead.
20To those who once disobeyed when the patience of God was waiting in the days of Noah, while an ark was being prepared, in which a few, that is eight souls, were saved through water. 21Baptism, which now saves you as its counterpart, is not a removal of the filth of the flesh but the pledge of a good conscience toward God through the resurrection of Jesus Christ.
This question guards against a thin view of the sacraments. The answer is the second sentence of Article VI of the Confession of Faith: the sacraments "are means of grace by which God works invisibly in us, quickening, strengthening and confirming our faith in him." Article XVI of the Articles of Religion says that God "doth work invisibly in us" through them. Both standards agree that something happens in the sacrament that is God's doing and that the eye cannot see.
The phrase means of grace is John Wesley's own, and he used it for the outward signs and actions God has appointed as the ordinary channels through which he conveys grace to people. The scripture references show the invisible work behind the visible sign. In baptism, Paul says, "we were buried with him through baptism into death, so that just as Christ was raised from the dead through the glory of the Father, we too might walk in newness of life" (Romans 6:4). The water is seen; the burial and rising with Christ are done "through faith in the working of God who raised him from the dead" (Colossians 2:12). Peter says the same: (1 Peter 3:21).
The Supper works the same way. Paul asks the Corinthians, (1 Corinthians 10:16). Jesus promises that "the one eating my flesh and drinking my blood remains in me, and I in him" (John 6:56), and adds, (John 6:58). The catechism names three effects of this participation. God quickens faith, that is, brings it to life where it was dead; he strengthens faith that is weak; he confirms faith that is wavering. All three are his work, received by faith.
For the life of the church, this teaching sets the tone at the font and the table. A Methodist comes to the Lord's Supper expecting to receive something, and the same expectation surrounds every baptism. Wesley taught that a person who wants faith should use the means God has given and wait for God to work through them, and the church's confession says he does.