[NKJV]
Jude 1:6; And the angels who did not keep their proper domain, but left their own abode, He has reserved in everlasting chains under darkness for the judgment of the great day;
Jude 1:7; as Sodom and Gomorrah, and the cities around them in a similar manner to these, having given themselves over to sexual immorality and gone after strange flesh, are set forth as an example, suffering the vengeance of eternal fire.
Apparently angels are capable of sexual immorality, and able to go after "strange" flesh (non-angelic flesh).
[AMP]
Jude 1:6; And angels who did not keep (care for, guard, and hold to) their own first place of power but abandoned their proper dwelling place--these He has reserved in custody in eternal chains (bonds) under the thick gloom of utter darkness until the judgment and doom of the great day.
Jude 1:7; [The wicked are sentenced to suffer] just as Sodom and Gomorrah and the adjacent towns--which likewise gave themselves over to impurity and indulged in unnatural vice and sensual perversity--are laid out [in plain sight] as an exhibit of perpetual punishment [to warn] of everlasting fire. [Genesis 19]
[GNB]
Jude 1:6 Remember the angels who did not stay within the limits of their proper authority, but abandoned their own dwelling place: they are bound with eternal chains in the darkness below, where God is keeping them for that great Day on which they will be condemned.
Jude 1:7 Remember Sodom and Gomorrah, and the nearby towns, whose people acted as those angels did and indulged in sexual immorality and perversion: they suffer the punishment of eternal fire as a plain warning to all.
[NASB]
Jude 1:6; And angels who did not keep their own domain, but abandoned their proper abode, He has kept in eternal bonds under darkness for the judgment of the great day,
Jude 1:7; just as Sodom and Gomorrah and the cities around them, since they in the same way as these indulged in gross immorality and went after strange flesh, are exhibited as an example in undergoing the punishment of eternal fire.