a. Worship is not simply singing
The word 'worship' is mostly used today as a synonym for singing. We see this whenever people call singing the 'Worship Time', or just 'worship', and call the song leader the 'Worship Leader'. Sometimes, 'worship' is distinguished from praise and narrowed to mean a particular kind of intimate singing to God.
The problem with this is that most of the biblical meaning of the word 'worship' gets lost - worship as service, worship as submission, worship as reverence. See Gathered for worship
b. Singing is not simply a ministry of the Word
Reacting against a simplistic equation of worship and singing, some insist that the function of a song in church is mainly to teach, and we should thus choose the songs that teach best, based on how well their contents reflect sound doctrine. According to Colossians 3:16, singing can certainly play an important role in edifying the church and helping us grow to maturity. See Building towards maturity in Christ.
But this is not a complete representation of the Bible's theology of song. Some psalms have a teaching function. For example, Psalms 105 and 106 put the history of Israel into verse. But didactic psalms are in the minority. Psalms 63, 138 and 150 are not very didactic at all. Paul's injunction in Colossians 3:16 about teaching and admonishing one another 'with psalms and hymns and spiritual songs' outlines one aspect of singing in church, rather than prescribing the only way in which it can be used.
There is a mixture of songs in the Old Testament - some sung to each other (with a didactic or exhortatory function), and some sung to God (to praise or exhort God directly. Some songs oscillate between both modes. To say that singing is fundamentally a ministry of God's word to us only captures one facet of this.
Singing is fundamentally a response to God from his saved people. At times, we 'respond' by singing to others (to exhort them to praise the Lord, or to teach them about the Lord) because both of these things bring praise to God indirectly. At other times, we will sing to the Lord directly. This latter type of singing is - in a sense - a sung prayer, and may sometimes be bold and declarative, and at other times personal and intimate, if the model of the psalms is anything to go by.
c. We do not sing to make God present
There are some contemporary songs which suggest that 'God is in this house' through praise. This is unhelpful, because it fails to recognise the biblical-theological shift which has occurred between the Old and New Testaments. God's presence is not located in an earthly temple anymore and therefore cannot be confined to a church building or a particular gathering of his people. We do not make God present through our praise, nor is God's presence to be confused with the emotional euphoria created by singing.
Faith is the means by which we draw near to God in heaven, trusting in his promises and relying on the mediation of Jesus our great high priest (Heb. 4:14-16; 10:19-21; 12:22-24). Prayer and praise are ways of expressing that faith and acknowledging his grace towards us in the Lord Jesus.