What are some examples of the "grand style" Milton uses in Paradise Lost, particularly from Book I?

The so-called “grand style” of John Milton’s epic poem is the
lofty, elevated, or non-colloquial phrasing he uses to add to the dignity of the poem and imply
the importance of its subject matter. Milton deliberately chose this style to fit the grand or
lofty topic he had chosen for his epic – nothing less than the fall of man and the justice of
God’s response to that fall. A more colloquial or “everyday” style of language would not have
seemed appropriate to such an inherently important plot and
theme.

Several elements help contribute to the “grand style” in
which Paradise Lost is written. They include the
following:

• A tendency to write in long, often complicated
  sentences, so that readers cannot simply breeze through the poem but must ponder it carefully. A
  good example of such a sentence is the very first sentence of the poem, which goes on for 16
  lines before the first period finally appears. Although the structure of this sentence is not
  especially difficult to follow, neither can that structure be called easy or instantly
  accessible. Milton’s sentences often flow on and on, adding a kind of majesty to the phrasing of
  the work.


• A tendency to allude, either overtly or indirectly, to
  the Bible and to classical literature. Since the Christian Bible and the Greek and Roman classics
  were among the most important texts of Milton’s culture, his habitual allusions to them instantly
  elevate the tone of his phrasing.


• A tendency to use a kind of
  sentence structure more common in Latin than in simple Anglo-Saxon English. For instance, in the
  first sentence of Paradise Lost, the very first verb does not appear until
  line 6. Instead of beginning the poem by writing, “Sing, Heav’nly Muse, of man’s first
  disobedience,” Milton does not provide the crucial verb “Sing” until line six. This postponement
  of the verb creates a kind of suspense, as we wonder what verb will make sense of the first five
  lines. Another superb example of Milton’s use of “Latinate” syntax, or sentence structure,
  occurs, in lines 44-45, where Milton, speaking of Satan says,
  

Him the
Almighty Power

Hurled headlong flaming from th’ethereal
sky.

An example
of the “grand style” at the beginning of Book 3 involves Milton’s reference to
Hell as the “Stygian pool” (14). Rather than simply referring to “Hell” or even to “Hades,”
Milton offers a classical allusion to enhance the grandeur and resonance of his language. Another
classical allusion appears two lines later, in the reference to “th’ Orphéan lyre” (17). This
tendency to discuss Christian ideas by alluding to classical precedents is typical of the entire
poem. Milton was steeped in the Bible, but he was also thoroughly familiar with the Greek and
Latin classics and used his classical learning to enhance the richness of his style. Thus in one
line he refers to the classical “Muses” (27), and then three lines later he refers to Biblical
“Sion” (30). This constant interplay of the classical and the Christian is one of the main
features of Milton’s “grand style.”

For an excellent brief overview
of the poem, please see C. S. Lewis, A Preface to Paradise Lost (Oxford:
Oxford University Press, 1961).