1. Symbols
Symbols function literally and figuratively at the same time.
“The shaggy dog buried its bone.” Dog is NOT a symbol in this case; it’s just a four legged creature.
“I would never date that guy; he is such a DOG!” Dog is NOT a symbol in this case. The speaker is not talking about a dog at all, therefore using a metaphor.
“You can’t teach an old DOG new tricks.” This famous idiom is not only talking about the animal, but also about living creatures of any age, and is therefore symbolic.

2. Two roads diverged in a yellow wood, And sorry I could not travel both And be one traveler, long I stood And looked down one as far as I could To where it bent in the undergrowth; Then took the other, as just as fair, And having perhaps the better claim Because it was grassy and wanted wear, Though as for that the passing there Had worn them really about the same, And both that morning equally lay In leaves no step had trodden black. Oh, I marked the first for another day! Yet knowing how way leads on to way I doubted if I should ever come back. I shall be telling this with a sigh Somewhere ages and ages hence: Two roads diverged in a wood, and I, I took the one less traveled by, And that has made all the difference. 
In The Road Not Taken, by Robert Frost, the roads take on a symbolic meaning. Yes, the speaker is looking at actual roads in the “yellow wood”, but the “road” concerns a choice the speaker must make. Although readers can’t discern the nature of the choice that must be made, it is enough if readers see an expression of regret in having to make a choice. Readers know that the speaker longs for the realms of the experience he has had to forgo.

3. Two roads diverged in a yellow wood, And sorry I could not travel both And be one traveler, long I stood And looked down one as far as I could To where it bent in the undergrowth; Then took the other, as just as fair, And having perhaps the better claim Because it was grassy and wanted wear, Though as for that the passing there Had worn them really about the same, And both that morning equally lay In leaves no step had trodden black. Oh, I marked the first for another day! Yet knowing how way leads on to way I doubted if I should ever come back. I shall be telling this with a sigh Somewhere ages and ages hence: Two roads diverged in a wood, and I, I took the one less traveled by, And that has made all the difference
Is the choice a choice between good and evil? Provide evidence.
Robert Frost