This traditional Irish blessing is an ancient Celtic prayer. Celtic literature is famed for using images of nature and everyday life to speak of how God interacts with with His people. For example, another famous Celtic prayer known as "St Patricks Breastplate" draws upon nature to describe the strength of God. Here's an excerpt:-
I arise today
Through the strength of heaven:
Light of sun,
Radiance of moon,
Splendour of fire,
Speed of lightning,
Swiftness of wind,
Depth of sea,
Stability of earth,
Firmness of rock.
"May The Road rise up to meet you" is about God's blessing for your journey - may your walk be an easy one - with no huge mountains to climb or obstacles to overcome.
It alludes to three images from nature - the wind, sun and rain - as pictures of God's care and provision. The "wind" can be likened to the Spirit of God, who came as a "mighty wind" at Pentecost. The suns warmth in the prayer reminds us of the tender mercies of God, "by which the rising sun will come to us from heaven" (Luke 1:78, NIV), whilst the soft falling rain speaks of God's provision and sustenance. Finally, we are reminded that we are held safe in God's loving hands as we travel on our journey through life. As such this prayer is a good blessing for wedding ceremonies.
May the blessing of light be on you
(Scottish Blessing Prayer)
May the blessing of light be on you, light without and light within. May the blessed sunlight shine on you like a great peat fire, so that stranger and friend may come and warm himself at it. And may light shine out of the two eyes of you, like a candle set in the window of a house, bidding the wanderer come in out of the storm. And may the blessing of the rain be on you, may it beat upon your Spirit and wash it fair and clean, and leave there a shining pool where the blue of Heaven shines, and sometimes a star. And may the blessing of the earth be on you, soft under your feet as you pass along the roads, soft under you as you lie out on it, tired at the end of day; and may it rest easy over you when, at last, you lie out under it. May it rest so lightly over you that your soul may be out from under it quickly; up and off and on its way to God. And now may the Lord bless you, and bless you kindly.