Why don't we use soda acid fire extinguishers to extinguish metal fires?

Explanation

(i) material used in soda and fire extinguisher
(ii) reaction that takes place in soda acid fire extinguisher
(iii) products btained
(iv) reaction between one of the products with metal that causes fire
(v) products obtained in the above reaction
(vi) effect of one of the products on the atmosphere