The Lutheran preacher uses the law of God to confront and convict the hearer of his faults and failures. When done well the hearer will believe the preacher is speaking directly to him and will recognize and repent of his sin.
The preacher also proclaims the peace and the comfort of the Gospel in all its glory. Pointing to God’s grace, and to the forgiveness of sins won for us by Jesus Christ through his death and resurrection, he lifts the hearer from the depths of sorrow and regret to the heights of joy and hope.
A good Lutheran sermon will always have a clear presentation of both God’s law and gospel, to the glory of God and the edification of the hearer.