This work aims to investigate the use of metaphors to provoke and sustain the dialogical and authoritative discursive process in the content of Sciences related to the preservation of water. Given this function to metaphors, one can observe the construction of meanings of the students from the alternation of these two discursive genres. The data collection was divided in two stages, in which the first one prevails the dialogic discourse and the second with predominance of the discourse of authority. The results obtained are also analyzed in these two stages, whose performances of students are reasonable in the construction of the intended meanings when aided this discursive form by the use of the metaphors used here
