The documentation of the benefits of blog use in foreign language education has proliferated since 2006. In the field of blogging to write, most studies focus on learners' linguistic performance and perceptions. To provide an analysis of learners' writing performance by using blogs, in addition to the often-researched areas, this study examines two further dimensions--learners' metalinguistic awareness and affective performance. This paper reports findings in these two areas. Twenty-six randomly selected, non-English majors participated in a conventional English writing class, forming the control group, while 18 students took part in a blog-integrated English experimental writing class. The results of comparison showed no significant differences between the two classes in regards to metalinguistic strategy use but there were significant differences in "metalinguistic awareness." It is conjectured that more exposure to the target language materials, the interaction and collaboration among students, the aid of the reverse-chronological order of blogs, and the integration of blogs in the writing class significantly enhanced students' metalinguistic awareness. In affective performance, there were no significant differences between the two classes in writing motivation and writing anxiety. Nevertheless, it was the control class that significantly surpassed the experimental class in writing self-efficacy.