The most obvious device used by Burns in this poem is personification: the entire poem is an address—or apostrophe—to a mouse, making the assumption that the mouse has human attributes, motivations, and understanding. Indeed, the most famous lines from the poem group the mouse together with humans as capable of "scheming": "the best-laid plans o' Mice an' Men / Gan aft agley."

The poem's structure utilizes a steady repeating rhyme scheme of AAABAB, which helps sustain its rhythm and internal cohesion. Burns also uses alliteration repeatedly: examples include "thou art no thy lane," "weary Winter," "cruel coulter." You will be able to spot other instances of this yourself.

We can also, arguably, spot a continuing metaphor in the description of the mouse's hole as "housie" and "cell." This continues the theme of personification, by which the mouse is addressed as if it is human and has equal regard for its home as people do. Burns suggests that we should have more consideration for our fellow mortal creatures, rather than assuming they are merely simple animals.

In "To a Mouse," by Robert Burns, a metaphor is used in the following lines:

A daimen icker in a thrave

'S a sma' request:...

To paraphrase:

An occasional ear of grain in a bundle is a small request. 

The mouse taking an occasional grain from the farmer's stash is compared to someone making a small request.  The tenor of the metaphor is the mouse eating a piece of grain, and the vehicle by which Burns describes the taking of the piece of grain is one person making a small request from another person.

Alliteration is used repeatedly:  "bickering brattle!" and "weary winter" are two examples. 

I'm probably missing it, but I don't see a simile. 

What are the linguistic devices used in 'To a Mouse' by Robert Burns and why are they effective?

In "To a Mouse," by Burns, the most important linguistic device used--the device that contributed to a change in literature and a new movement in literature--is the Scottish dialect.

His use of common language for well-written, serious poetry--his poetry is serious, even when his subject is a mouse or a louse--is a rejection of neoclassicism, and ultimately helped pave the way to Romanticism. 

Burns uses a regional Scottish dialect used only by a relatively few Scots, and thereby brought poetry to the common people.  He rejected any view of poetry as elitist and only for the learned. 

Along with the dialect, his subject is also common--a farmer in a field who cuts through a mouse's home.  Yet he manages to deal with universal ideas--such as the futility of human intentions.  

What are the linguistic devices used in 'To a Mouse' by Robert Burns and why are they effective?

In this poem, the poet comes upon a little mouse while he is plowing his field. So, he employs a type of apostrophe - he addresses the mouse. The mouse is actually present, but obviously is not human and cannot understand the poet, so he also uses personification to attribute human qualities that the mouse does not possess. Then, there is a prolonged imagery in which the poet presents the mouse as a hard-working creature who must continually rebuild her house and who does not ask much from life - just a small ear of corn now and then. He then identifies with the mouse:

But Mouse, you are not alone,
In proving foresight may be vain:
The best laid schemes of mice and men
Go often askew,
And leaves us nothing but grief and pain,
For promised joy!

He states that like the mouse, sometimes man's plans don't work out either (Steinbeck borrowed these lines for the title of his novel Of Mice and Men).

Finally, he concludes:

Still you are blest, compared with me!
The present only touches you:
But oh! I backward cast my eye,
On prospects dreary!
And forward, though I cannot see,
I guess and fear!

He says that the mouse is blest compared to man, for man must look back on his past with regret and man cannot see the future so he fears it, whereas the mouse is only concerned with the present.

Do you think these devices are effective? Does it make the poem come alive more by using a mouse as a vehicle to express such philosophical thoughts?

Read about Robert Burns here on eNotes.