The Bible calls Jesus our mediator:
Christ Jesus is the one who died—more than that, who was raised—who is at the right hand of God, who indeed is interceding for us. (Romans 8:34, ESV)
For there is one God, and there is one mediator between God and men, the man Christ Jesus, (1 Timothy 2:5, ESV)
Consequently, he [Jesus] is able to save to the uttermost those who draw near to God through him, since he always lives to make intercession for them. (Hebrews 7:25, ESV)
Trinitarians believe that Jesus intercedes with the Father on our behalf. He can do this because he is a distinct person, and he is the only competent mediator because only God can truly mediate with himself.
Modalism teaches that the Father, Son and Holy Spirit are "different modes or aspects of the One God, as perceived by the believer, rather than three coeternal persons within the Godhead." (Wikipedia)
If God is not multiple people, how can Jesus intercede with the father? How do modalists understand the role of Jesus as mediator?