GLORY be to God for dappled things—
For skies of couple-colour as a brinded cow;
For rose-moles all in stipple upon trout that swim:
Fresh-firecoal chestnut-falls; finches' wings;
The poem begins with a strong,  declarative  statement. This is emphatically a poem of praise to God for things that are “dappled”, meaning spotted or mottled or stippled. The line ends with a dash, a definitive  end-stop  that creates a  caesura  or pause for the reader to reflect and share the poet’s sense of wonder. 
 The hard,  alliterative  “g"s have a solid, ringing quality, like a prayer or hymn or psalm. The line is an  inter-textual  echo of  Psalm 148 
 Praise ye the LORD. Praise ye the LORD from the heavens: praise him in the heights. 
 This is appropiate, given that the motto of Hopkins' religious Order, the Jesuits, is “Ad Maiorem Dei Gloriam”, meaning, “For the greater glory of God.” 
 
 The line is a good example of the metrical style invented by Hopkins that he called  sprung rhythm , where traditional, regular  metrical patterns  are replaced by a mix of strong, stressed syllables and a varied number of unstressed syllables. 
 Here the stresses are on the first syllable of “Glory”, on “God”, on the first syllable of “dappled” and on “things”. This creates a rhythmically uneven but buoyant quality that sets the tone of the poem.