Prior to the events of Ignition, there was a sort of romance triangle between Jaller, Hahli and Matoro. Jaller, of course, had a thing for Hahli, but he usually tried too hard and made a fool of himself. Hahli, on the other hand, had a flirty relationship with Jaller but only ever saw him as a really good and trustworthy friend. Hahli was more interested in the enigmatic hunter and explorer, Matoro. However, Matoro was more or less oblivious to Hahli's interest in him as anything more than a friend, and was also blind to Jaller's jealousy of him, despite their friendship.
After being transformed into Toa, however, Jaller and Matoro came to the agreement that since they were both comrades with Hahli on the same Toa team, they couldn't afford to have an underwritten rivalry, especially for one of their comrades.
This could explain why Jaller and Matoro have such a good relationship as Toa of Fire and Ice, respectively; in addition, it explains the bond the three of them share on their Toa team, a bond that seems to be better between these three than with Kongu, Hewkii and Nuparu.