There are different categories of psalms based upon their themes
The Chronicler wrote that David appointed some Levites to minister before the ark of the Lord, to celebrate and to thank and praise the LORD God of Israel (1 Chronicles 16:4). There are also different kinds of Psalms. The classification varies with different scholars. This is a simplified classification. As a note of caution regarding what are called messianic psalms, we must be careful not to read into a psalm more than the author understood or meant. The New Testament author under inspiration used psalms for his purpose, but this use was often different than the original author understood.
- Imprecatory psalm in which the author asks God (not man) to judge sin, condemn the wicked, and show his righteousness (e.g. Psalm 7, 35, 55, 58, 59, 69, 79, 109, 137, 139).
- Lament psalms, individual and national, in which a person or the nation asks God for help during a failure, testing, or disaster (e.g. Psalm 3, 12, 13, 44, 85).
- Messianic psalms, in which the psalmist speaks in some way of the coming messiah (Psalm 110). Messianic predictions are based in the hoped for ideal Davidic king. Some refer to the historical scene at the time of writing but apparently also have a clouded reference to the coming messiah. These do have historical reality, but the Messiah is the one through whom the ideal Davidic ruler is completely realized (e.g. Psalm 2, 22, 45, 72, 69, 132).
- Penitential psalms, in which one confesses sin to God and desires forgiveness and blessing (e.g. Psalm 6, 32, 51).
- Royal psalms proclaim God the king (e.g. Psalm 2, 72, 93, 97, 99, 132).
- Thanksgiving, praise, and declaration psalms (e.g. Psalm 19, 92, 103-106, 112, 113, 135, 136, 145-150).
- Wisdom psalms share features of wisdom literature. Wisdom psalms contrast the godly with the ungodly, emphasize Scripture, indicate that the ungodly will face judgment and the godly will be vindicated, use the “blessed is” formula, and share certain terms like “way,” “know,” “righteous,” “wicked,” “meditation,” “law,” “prosper,” “scorner,” and so on (Allen Ross, Notes on Psalm 2).
- The best known psalm (Psalm 23) is difficult to classify. Allen Ross says that Hermann Gunkel's description as "a psalm of confidence" is good (Ross, A Commentary on the Psalms, Vol 1, p 555, referring to Gunkel, The Psalms, p 35).