The natives in the Solomons were largely neutral at the beginning of the war, as they didn't feel invested in the conflict and generally took a "wait and see" approach. In many instances, they had been interacting with colonial government, missionaries, and plantation owners for years and so had some experience with and loyalties to the Australians and New Zealanders. These prior relationships were helpful, but were not a guarantee of continuing loyalty. Martin Clemens (the British colonial official and coast watcher on Guadalcanal) writes in Alone On Guadalcanal about his pervasive fear that the natives would turn him into the Japanese. He relied on his personality and key natives to hold his alliance together. He needed a team of native porters to move his radio and gear farther into the mountains in order to stay ahead of the Japanese in the first few months of the Guadalcanal invasion. This support was critical for him as well as all the other coast watchers on the other islands. The coast watchers provided critical intelligence for the Allies and were often completely dependent on native support.

In most cases, the fighting on the islands took place largely near the coasts. The natives would usually move their families away from the fighting to wait out the conflict. In places like New Guinea, an area so large and often inhospitable that the fighting rarely moved inland, the tribes in the interior barely knew a war was taking place.

All the combatant armies needed and relied on native workers. The Japanese, taking the stick over the carrot approach as they often did, alienated many tribes at the beginning of the conflict with indiscriminate violence. This was greatly to their detriment. In some areas (Bougainville? New Britain?) the Japanese found themselves embroiled in a long-running guerilla war with the natives, in addition to fighting the Allies.

A couple of books on the subject:

Lonely Vigil by Walter Lord

Alone On Guadalcanal by Martin Clemens

Touched With Fire: The Land War in the South Pacific by Eric Bergerud

Also, check out Jacob Vouza on google. Crazy story about a native who fought on Guadalcanal.

To pickup on what the earlier poster said, how the Melanesians view both the Japanese and Americans were mixed but I would like to add that the interaction greatly affected by the vast surplus of military supplies.

Some of the Melanesians were indeed incorporated into the colonial economy but this was really only at best a small minority. The plantation economy of the Solomon Islands had collapsed in the 1920s and 1930s and had been effectively abandoned by the Europeans. Most of the Melanesians returned to a traditional way of life which worked but was also an extremely sparse life devoid of substantial possessions.

When the Japanese, Australians and Americans landed they brought with them substantial stores of food, clothing, advanced technology and hand tools like shovels. Much of this was scavenged by the Melanesians or given to them as gifts or just as basic acts of kindness.

The arrival of this stuff, referred to as 'Cargo', was hugely transformative to local cultures. Melanesians had no way of producing the goods and the raw amount of them overwhelmed the traditional reality of property. All of this was very disruptive, but frankly in a good way because these cultures were very poor.

Food was a big deal. It is a complete misnomer that less advanced societies have more food than more advanced societies. We have several examples of less advanced societies having more food (like Jamestown) but in reality the superior production and storage capacities of more advanced societies gives those societies huge advantages in the availability of food.

The average Melanesian was borderline starving and at best eating a meager diet of fish and local edibles. All of the combatants brought in large stores of food (particularly the U.S.) and this food made it into the hands of the locals. For this reason many of the islanders actually viewed the war as a 'good thing' as it brought up their standard of living so drastically.

As to seeing large sea battles, dogfights and so forth...no the islanders had seen nothing like that.