Psalm 34 (Psalm 33 in the venerable Douay translation) is a short prayer, full of beautiful phrases with deep meaning.  In his commentary, St. Jerome (d. 420) considers this psalm as about prayer.  The verses used for the psalm at Mass are presented below, with St. Jerome's commentary on them.  The translation of the psalm verses follows the Latin version which Jerome uses, and which differs slightly from the modern English version.  The antiphon is treated last.

" 'I will bless The Lord at all times.'  That is, in prosperous and in adverse times.  David did this, and now the Church does it.  'His praise shall ever be in my mouth.'  I will always praise God with mouth, heart, and intent mind.

" 'Glorify The Lord with me.'  Praise The Lord, the Father.  'Let us together extol his name.'  As though the Prophet [David] were to say: As I love him, so you should do, likewise.  'Let us together extol his name.'  The Name which the Father gave to his Son, which is above every name.

" 'Approach The Lord.'  Believe in him.  'Approach The Lord', not in terms of place, but in your faith and good works.  'And be enlightened."  That is, understand with your mind.  Unless you believe, you will not understand.  'And your faces may not blush with shame.'  That is, in the judgment on the last day, when the wicked will be ashamed in their condemnation.  

" 'When the poor one called out.'  Christ the Lord, who was made poor for us, called out to his Father during his Passion.  The Church calls out now.  'And from all his distress he saved him.'  Raising him from the dead.  

" 'The angel of The Lord encamped around those who fear him, to deliver them.'  That is, the Angel of great counsel which he gave to them.  It is beyond doubt that those who fear The Lord are protected by angels.  As The Lord himself teaches in the Gospel [Matthew 18, 10]: 'Amen, amen, I say to you that their angels daily behold the face of my Father who is in heaven.  Therefore, those who fear God with purity of heart will be surrounded as with a wall by an angelic guard.

" 'Taste and see that The Lord is sweet.'  When a person begins to fear and begins to keep the commandments, he will know that The Lord is sweet, for he is the Living Bread that gives fullness to this world.  Blessed is he who trusts in him, and not in uncertain riches."