The family Metaviridae is a member of the order Ortervirales which consists of five reverse-transcribing virus families (Krupovic et al. 2018). These viruses are comprised of retrotransposons that in general have 50% of nuclear DNA content and transpose by reverse transcription as an RNA intermediate. Major important differences between retrotransposons in plants compared to other eukaryotes include often high copy numbers, their extensively heterogeneous populations, and their chromosomal dispersion patterns (Kumar and Bennetzen 1999). The foundation for the taxonomic classification of the family Metaviridae, specifically in terms of the plant infecting viruses, was placed through several historical studies. For instance, a retrotransposon related to Ty3 of yeast and the gypsy group of Drosophila was detected from Lilium henryi (Lili) (Lilium henryi Del1 virus) (Smyth et al. 1989). Moreover, a retroelement element was characterized from the genome of L. henryi and found that the organization of the element named del has characteristics of retrotransposons such of the Copia family of Drosophila and Ty gene of yeast (Sentry and Smyth 1989). Members of the family Metaviridae include viruses infecting fungi, plants, and animals. Metaviridae consists of 2 genera, namely, Errantivirus and Metavirus, comprising 10 and 21 species, respectively (Llorens et al. 2020). The typical member of Metaviridae is comprised of Ty3 virus infecting Saccharomyces cerevisiae (species Saccharomyces cerevisiae Ty-3 virus). Virions comprised of icosahedral (T = 9) and may have enveloped genomes. Only the genus Metavirus includes plant infecting viruses and, thus, will be further discussed in this chapter.