Hallidayan grammatical metaphor can conventionally be dichotomized into ideational metaphor and interpersonal metaphor. The paper,based on grammatical metaphor,probes into the theories concerning textual metaphor,and then focuses on explorations on five typical realizations of textual metaphor in English such as Thematic Equative. It is found that the factual existence of textual metaphor proves that textual metaphor is an indispensable part of grammatical metaphor and coexists with ideational metaphor and interpersonal metaphor.