Understanding Anim Zemiros
Shir HaKavod – The Hymn of Honor – is better known by its opening words, Anim Zemiros (“I will compose pleasant songs”). The song is popularly attributed to Rav Yehuda HaChasid, though it was more likely composed by his father, Rabbi Shmuel ben Kalonymus HaChasid of Speyer (12th century), who also composed Shir HaYichud (The Song of Unity). Shir HaKavod is a series of couplets (except for the last line) that describe what God metaphorically “looks like.” Accordingly, the song is replete with imagery from the Books of the Prophets.
There are a number of different practices regarding how often this song should be recited – only on Yom Kippur, Rosh Hashana and Yom Kippur, all Festivals, Shabbos and Festivals – but the current practice is to discourage its recitation daily. This is because of the song’s great holiness. If it were recited daily, it would become routine and we would not open the ark for it. (Compare the way we open the ark for Aleinu on Rosh Hashana and Yom Kippur but not as part of the daily service.)
It should be noted that, in the portion of the song describing God, when the author speaks in the first person, he is not actually speaking autobiographically. When he says things like "He delights in me" and "my adornment is on Him," the author is speaking as the nation of Israel personified.
Following is a translation of Shir HaKavod, including notes indicating references to Biblical verses and occasional Talmudic dicta. While not exhaustive, this will hopefully shed additional light on the meaning, depth and beauty of this beloved part of the liturgy.
I will compose pleasant songs and weave poems  because my soul longs for You. My soul desired the shadow of Your hand,  to know every one of Your secrets.
When I speak of Your glory, my heart longs for Your love. Therefore I will speak about You and Your glories. I will honor Your Name with songs of love.
I will tell of Your glory, though I cannot see You. I will describe You metaphorically, though I cannot truly know You. Through Your prophets, through counsel with Your servants, You gave us the metaphors for the beautiful glory of Your power.
They described Your greatness and Your strength through Your powerful deeds. They described an allegory of You, not how You really are. They described You according to Your deeds.
They spoke of You metaphorically in many different visions; nevertheless You are One in all these different forms. They pictured You in advanced age and in younger days,  the hair of Your head as that of an old man and black as in youth.
An elder on judgment day and young in battle, like a skilled warrior. He wears salvation like a hat;  Salvation is His, through His right hand, His holy arm.
His head is covered by dew of light,  the locks of His hair are the rains of night. He will take glory through me because He delights in me. He will be the crown of my pride.
The finest pure gold is a form for His head;  inscribed on His forehead  is the glory of His holy Name. For grace and honor, the pride of His splendor.  His nation crowns Him with their prayers.
The locks of His hair  are like those of a youth; His tresses are the blackest curls. The place of righteousness  is the pride of His splendor; May He raise it above His greatest joy! 
His treasured people will be like a crown in His hand,  like a royal tiara, the pride of His splendor. He carried them from infancy  and wore them like a crown.  He honors them because they are precious to Him.
His adornment is on me and my adornment is on Him.  He is always nearby when I call upon Him.  He is both white and red.  His garment is red from treading the press on His way from Edom. 
He showed the knot of His tefillin to His humble servant  - a likeness of God before his eyes.  He desires His people; He will glorify the humble. Enthroned upon their praises,  He glorifies among them.
The beginning of Your word is truth,  called from the beginning.  In each generation, the nation delves into knowing You. Please accept my songs before You and draw my joyful praise close to You.
May my praise be a crown for Your head; may my prayers be accepted like the Temple incense. May the poor person's song  be precious in Your sight, like the songs that were sung over Your sacrifices.
May my blessing rise to the head of the One Who sustains all,  the One Who creates and gives life, righteous and mighty.  Please nod Your head to acknowledge my blessing;  accept it for Yourself as You did the finest incense.
May my words be found sweet before You, as my soul longs for You. 
- Weave poems – Why is the author “weaving” this song? With praises, he is metaphorically creating a “garment of honor” for God (which is why the song is called The Hymn of Honor). This is expressed in Psalms 93:1, “God reigns, clothed in majesty.” The explanation of the verse is, “When is God clothed in majesty? When His children acknowledge His sovereignty,” as the author does through these praises.
- My soul longs for You – as in Psalms 42:2, “As a hart longs for water, so my soul longs for You, God.”
- Shadow of Your Hand – The “shadow of God’s hand” is a metaphor for God’s protection employed twice by the prophet Isaiah. In Isaiah 49:2, he writes, “He made my mouth like a sharp sword; He hid me in the shadow of His hand. He has made me a polished shaft and concealed me in His quiver.” In Isaiah 51:16, God says, “I have put My words in your mouth and covered you with the shadow of My hand so that I might plant the heavens, lay the foundations of the earth, and say to Zion, ‘You are My people.’”
- They pictured You in advanced age and in younger days – The Mechilta (parshas Shlach) relates that God appeared at the Red Sea like a mighty warrior as per Exodus 15:2 (“God is a Man of war…”), but at Sinai He appeared as an elder full of mercy, derived from Exodus 24:10 (“they saw the God of Israel”). Nevertheless, whatever capacity He exercises, He is One (“God is His Name” - Exodus 15:2 again).
- He wears salvation like a hat – The verb “to wear” in this verse is ChVSh. This is the verb used in Ezekiel 24:17, when God tells the prophet to continuing putting tefillin on his head even though he is in mourning. We see from this that it is an appropriate verb to use for donning headwear.
- Dew of light – This is another metaphor employed by Isaiah. In Isaiah 26:19, he writes, “Your dead will live, my corpses will arise - awake and sing, you who dwell in the dust! - for Your dew is like the dew of light, and the earth will bring the deceased to life.”
- The finest pure gold is a form for His head – as in Shir HaShirim 5:11, “His head is the most fine gold….”
- Inscribed on His forehead – At first glance, this would appear to be a reference to the tzitz (headplate) worn by the Kohein Gadol, which had the name of God inscribed upon it (see Exodus 28:36-38). More likely, it is a reference to Pirkei d’Rabbi Eliezer (chapter 4), which says that God sits in Heaven “on a throne, high and exalted… The appearance of His Glory is the color of amber. The adornment of a crown is on His head with His Explicit Name (YHVH) upon His forehead.” On a deeper level, this may be an allusion to Isaiah 4:2, “On that day, the sprout of God will be for pride and honor…” “Tzemach” (sprout) being an anagram of “metzach” (forehead), the forehead of God will display His pride and honor. (If this interpretation seems a stretch, please note that both this verse in Isaiah and this couplet of the song mention tzvi/pride, kavod/honor, and tiferes/tifara/splendor.)
- The pride of His splendor – These words, “tzvi tifara,” refer to Isaiah 28:5: “On that day, the Lord of Hosts will be for crown of pride (tzvi) and a tiara of splendor (tifara) to the remainder of His people.”
- The locks of His hair – The word “machl’fos,” translated here as locks, could mean braids. See Judges 16:13, regarding how Samson wore his hair in seven machl’fos.
- The place of righteousness – Jerusalem (see next note).
- Above His greatest joy – As per Psalms 137:6, “May my tongue cleave to the roof of my mouth…if I do not place Jerusalem above my greatest joy.”
- His treasured people will be like a crown in His hand – a reference to Isaiah 62:3, “You will also be a crown of beauty in the hand of Hashem, and a royal tiara in the open hand of your God.”
- He carried them from infancy – as per Isaiah 46:3, “Listen to Me, house of Jacob and the entire remnant of the house of Israel, who are carried (by Me) from birth and borne from the womb.”
- Wore them like a crown – a paraphrase of Job 31:36, “I would surely carry it on my shoulder; I would wear it like a crown.”
- His adornment is on me and my adornment is on Him – Tefillin are called an adornment (p’eir) several places in the Book of Ezekiel, including chapter 24, verses 17 and 23. We wear tefillin containing praises of God; the Talmud (Brachos 6a) tells us that God wears tefillin containing praises of Israel (“Who is like Your people Israel, a singular nation in the land?” – I Chronicles 17:21).
- He is always nearby when I call upon Him – “God is close to all who call upon Him…” (Psalms 145:18).
- He is both white and red – Shir HaShirim 5:10: “My beloved is white and red, prominent over ten thousand.” White symbolizes God’s attribute of mercy and red symbolizes His attribute of justice. (See next note.)
- His garment is red from treading the press on His way from Edom – The image of God’s clothes being red from treading a wine press in Edom are likewise metaphors from the Book of Isaiah. Isaiah 63:1-3 reads, “(1) “Who is that coming from Edom with garments dyed red from Batzra? Who is glorious in his apparel, stately in the greatness of His strength?” “It is I, the One Who speaks in victory, mighty to save.” (2) “Why are Your garments red, and Your clothes like those of one who treads in the wine vat?” (3) “I have tread the winepress alone; there was no one of the nations with Me. Yes, I tread them in My anger and trampled them in My fury. Their lifeblood is splattered on My clothes and I have stained all My garments.” (The reason God’s garments are completely red here, rather than the usual red mixed with white, is because in this instance He has exercised strict justice rather than justice tempered with mercy.)
- He showed the knot of His tefillin to His humble servant – Moses is the humble servant, as per Numbers 12:3 (“The man Moses was very humble, more so than any person on the face of the Earth”) and 12:7 (“My servant Moses…is trusted throughout My house.”). In Exodus 33, Moses asked to see God’s face (a metaphor for understanding His ways) and God showed him His back. The Talmud (Brachos 7a) tells us that this was the knot of God’s tefillin.
- A likeness of God before his eyes – That Moses could perceive God clearly is found in Numbers 12:8, “With him, I speak face to face, plainly and not obscured.”
- Enthroned upon their praises – as in Psalms 22:4, “You are holy, enthroned upon the praises of Israel.”
- The beginning of Your word is truth – This refers to the Torah. The second through fourth words of the Torah are “bara Elokim es,” whose final letters spell “emes” (truth). We see from this that God’s word, the Torah, starts with truth.
- Called from the beginning – A reference to Isaiah 41:4, “Who has caused and done this? The One Who called the generations from the beginning. I, Hashem, am the first and the last; I am He.”
- The poor person's song – The author asks that his song be accepted like the songs sung over the sacrifices in the Temple. These were “rich songs,” while our songs are “poor songs” because we offer them empty-handed. Additionally, the word used here for poor, rash, is an abbreviation for the author’s name, Rabbi Shmuel. So, on another level he is asking, “May Shmuel’s song be accepted….”
- Blessing rise to the head of the One Who sustains all – The idea of the author’s blessing reaching the head of God, referred to here as the Sustainer, is adapted from Proverbs 11:26, “If a person withholds grain, the people shall curse him; blessing will be upon the head of one who sustains (others with it).”
- Righteous and mighty – The word kabir, translated here as “mighty,” is fairly obscure. It appears ten places in Tanach, in Isaiah and Job. Examples include Isaiah 16:14 (“…the remnant shall be very small and without strength”) and Job 31:25 (“…my hand had received much”), where it means “abundant.” In Job 34:17, it is juxtaposed with tzaddik (righteous) as it is here.
- Please nod Your head to acknowledge my blessing – The idea of God nodding His head to acknowledge a blessing is found in Talmud Brachos (7a): Rabbi Yishmael ben Elisha had been the Kohein Gadol (High Priest). He related that he had once entered the Kodesh HaKodashim (the Holy of Holies) to offer the incense. On this particular occasion, he saw a vision of God on His throne, and God asked him to bless Him. Rabbi Yishmael’s blessing was, “May it be Your will that Your mercy overpower Your anger…and that You treat Your children with mercy….” God responded by nodding His head.
- My soul longs for You – The last line ends the poem as the first line began it, with “my soul longs for You.” The author returns to the same theme because of a lesson learned from Talmud Brachos (10a), “Any subject (in Psalms) that was precious to David begins with ‘ashrei’ (meaning ‘happy’ or ‘fortunate’) and ends with ‘ashrei.’”