There is a lot of reference to blood in Macbeth. Does the blood have a metaphorical meaning?Do you have any quotes that support this?
Blood is definitely a motif in Macbeth. The metaphorical/symbolic meaning of blood throughout the play is somewhat up to interpretation. I would say that there are a few things you could argue about this.
For example; blood could be considered an outward manifestation of the inward guilt felt by the Macbeths. The conversation that Lady Macbeth and Macbeth have after Duncan's murder is a good indicator of this. Lady Macbeth talks about washing the blood away by saying "a little water clears us of this deed". This shows that she does not feel the guilt of the murder at this time. Macbeth, on the other hand, believes that instead of water washing the blood off his hands, his hands could turn an entire ocean red with blood.
Your interpretation of the significance of blood can be defended with many quotes. I've linked below to Shakespeare navigator, which shows quotes from the play containing the word "blood".
Though the word does not even occur, the idea or image is present even to inundation, a flood of blood, such as spurts from a stuck pig. The same thing is true of Lady Macbeth's ghastly, "Yet who would have thought the old man to have had so much blood in him?" (V.i.45), and accounts - along with the coarse insolence of her reference to the King, guest, benefactor, as "old man" - for the power of this celebrated line. We have blood not only everywhere, then, but swarming. Moreover, in a number of other very powerful passages, the audience or reader is compelled to imagine blood for itself even more specifically than in the "swine" passage. "It will have blood, they say; blood will have blood," Macbeth mutters to himself (III.iv.122). Here the mysterious "It" is explained immediately - murder cries out for retribution - and yet the force of its initial, dreadful vagueness is not dissipated by the explanation. The horrible suggestion is in fact made by the explanation that anything in the universe not at once identified as something else is blood; and iteration of the actual word thrice in one line assists the suggestion. As a man thinks of his wife not by name but as "she" and "her", so Macbeth thinks of his topic - blood, the murder - as "it": central, permanent, a point to which other things are referred. The implied picture of his mind makes one shudder.