The main theme of Robert Burns's poem "My Heart's in the Highlands" is what the title indicates: his love for the Scottish Highlands. The poem expresses a sort of sentimental patriotism based on love of both idealized national character and landscape.
The first person narrator of the poem appears to be a member of the Scottish diaspora. Burns was writing in the eighteenth century in the wake of two major events leading to waves of emigration from Scotland.
The first event was the failure of the Jacobite risings, which in Scotland had religious and nationalistic roots. Many of those on the losing side fled to avoid losing their property -- or their heads.
Next were the Highland Clearances, in which landlords began clearing land to establish large-scale sheep farms. Many of the displaced and impoverished tenants left Scotland.
In addition to the forces of poverty and political and religious upheavals driving people away from Scotland, the availability of land in North America added a positive incentive, as the colonies were know as a place where people could make a life and fortune for themselves by dint of their own hard work.
The poem lists in fairly general terms the things members of the diaspora might miss about Scotland.
With many of his poems written in the Scottish dialect and modeled after old Scottish ballads and songs, Robert Burns conquered the hearts of his countrymen as he became their voice. The Scots found his dialect, his songs, and the cadence of his poetry to be the very fiber of their own hearts."My Heart's in the Highlands" has a theme that is very simply this: The love of my country and a nostalgia for the beauty of Scotland. Shakespeare once wrote, "Praising what is lost/Make the remembrance dear."
This is the meaning of Burns' song: When I call to my mind the beauty of Northern Scotland
...the mountains high cover'd with snow,
...the green valleys below,
...the forests and wild-hanging woods,
...the torrents and loud-pouring floods!
I am there again; I am there with a heart that feels too big for my body because this is the land that I love, this is my childhood, my youthful follies and loves, my family--all that is I.