Art by definition is “the expression or application of human creative skill and imagination”. So I’d say that memes are indeed art, as they are human made ways to express something via their own imagination. Additonal reasons memes can be art are found here: Are Memes our Era’s defining artistic movement? – Muckle Hen Blog
Can Memes be used for storytelling? If so, How?
Memes can indeed tell a story as it is quite literally making a long story short. It can get a point across a make everything clear without overexplaining everything.
Is it good for communication? Are they forms of self expression or are they more?
Memes are used for self expression, however its purpose isn’t restricted to this. It can be used to get a point across by using an image and caption to describe certain aspects that would be rather tedious to describe in words.