All of Heb 5 forms a chiastic structure with part of Heb 4:
1a) Heb 4:12-13, The word of God is living and powerful, discerning the thoughts + intents of the heart;
1b) Heb 4:14, Our great High Priest, Jesus the Son of God + hold fast to our confession;
1c) Heb 4:15, Our High Priest sympathizes with our weaknesses, being tempted as we are, yet without sin;
central axis) Heb 4:16, “Let us therefore come boldly to the throne of grace, that we may obtain mercy and find grace to help in time of need;”
2c) Heb 5:1-3, High priests among men have compassion for weaknesses + offer sacrifices for sins;
2b) Heb 5:4-11, High priests called by God, so also with Christ the Son, according to the order of Melchizedek:
2a) Heb 5:12-14, The word of righteousness is solid food for the mature, exercised to discern good and evil.
Jesus our High Priest is the living and powerful Word of God made flesh. He discerns the thoughts and intents of our hearts, yet sympathizes with our weaknesses, since He too has been tempted with the same weaknesses as we are. Even though He is the Son of God, He learned obedience by the things He suffered. In other words, He suffered while being tempted; He suffered with the weaknesses of the flesh that did not want to obey God. But He chose obedience to God despite suffering in every case.
Therefore, let us come boldly to the throne of grace. Our great High Priest, who sympathizes with our weaknesses, will grant us mercy toward our weaknesses, and also give us grace in our time of need, our time of temptation, to choose obedience to God as He did. Temptation is not the time to run from God, but straight to Him with confidence, and He will send us mercy and grace to help us through it.