It is clear from Angelou's choice of language that the "caged bird" of the title is not happy with its lot. There is a sense that he is restrained and prevented from fulfilling his true potential, seen in words like "clipped," "tied," and "bars." That this makes the bird angry is indicated by its way of moving—it "stalks"—and the "bars of rage" through which it can barely see.
The bird is frightened, too, unsure of what the future will hold for it—its singing voice is "fearful," and while it yearns to leave its cage in favor of things it has "longed for," it cannot see into the "unknown." The theme of this poem is one of being denied freedom, and this is encapsulated in the image of this bird, whose song is heard beyond the bars of the cage which traps it; it may be angry at its confinement and unsure of how to escape its cage, but its spirit has not been killed.
Sometimes, the plight of the caged bird can seem hopeless—it stands on "the grave of dreams," suggesting that it has made attempts before to reach what it longs for, but these attempts have been thwarted by circumstances. Words such as "shouts" and "nightmare scream" express the sheer pain the bird has felt and has tried to articulate. However, the tenacity of the bird is shown through the fact that it continually "opens its throat to sing," despite everything that has wounded it in the past. Its song is heard far beyond the cage in which it is confined, with the poem ending on a hopeful note—the bird, a metaphor for oppressed people, may be entrapped and thwarted by society, but its longing for freedom can never be stamped out of it.