The main similarity that links many of the odes of John Keats is that they alll represent the character of typical Romantic poetry in theme. He writes in vivid and imaginative style for example about the passing of time and how we cannot go back, nature's beautiful and exquisite bounty towards us as humanity, the sorrow of loneliness or silence of perfect alone-ness as well as the slightly more sentimental expression of depression. There is also an undercurrent of the expression of his love of all things Greek and his understanding of Classical ideas. Beautiful symbolism and imagery are another characteristic. Unfortunately, the genius of Keats was not realised or appreciated by his peers at the time, and it is said that he was ignored, cold-shouldered and humiliated by his 'betters.' You will now need to go through some of the odes and note similarities in style, form and rhythm and how they express the above themes.