Metaviridae are a family of viruses which exist as retrotransposons in a eukaryotic host’s genome. They are very closely related to retroviruses: Metaviridae share many genomic elements with retroviruses, including length, organization, and genes themselves. This includes genes that encode reverse transcriptase, integrase, and capsid proteins. The reverse transcriptase and integrase proteins are needed for the retrotransposon activity of the virus. In some cases, virus-like particles can be formed from capsid proteins.
Some assembled Metaviridae particles can penetrate and infect previously uninfected cells. An example of this is the gypsy, a retroelement found in the Drosophila melanogaster genome. The ability to infect other cells in determined by the presence of the retroviral env genes which encode coat proteins.