Time
The character of Time appears in Milton's seventh sonnet. In this poem, Time is a sort of villain, stealing years from the narrator and forcing him to grow older into a man.
Patience
Patience features in Milton's famous Sonnet XIX. In this sonnet, the narrator is lamenting the fact that his blindness makes him unable to write, and therefore useless to God. However, the character of patience reminds the narrator that he does not need to be actively working to serve God, he can simply honor God in his heart and wait.
God
God is present in many of Milton's poems due to Milton's religious devotion. His poems often promote religion and God's glory either overtly or more subtly.
Narrator
The narrator, which can usually be assumed to be the voice of Milton himself, is present in all of the poems. In some, the narrator addresses a more general audience while in others, he speaks to a specific person he knows more intimately. Milton's narrator is especially God fearing and religious.
Audience
The audience is the "you" and the unspoken listener that the narrator addresses. As a character, it can be interpreted as either the reader or a specific person the narrator is addressing who is better known, such as a close friend or lover.