ʻO ka huʻa metala he hale paʻa i loko o ka metala paʻa (ke alumini pinepine) me nā pores piha piha i ke kinoea i loko o kahi hapa nui o ka leo. Hiki ke hoʻopaʻa ʻia nā pores (closed-cell foam) a i ʻole i hoʻopili ʻia (open-cell foam). He porosity kiʻekiʻe ka hiʻohiʻona wehewehe o nā huʻa metala: maʻamau, ʻo 5-25% wale nō o ka leo ka metala kumu, hana i kēia mau mea ultralight. ʻO ka ikaika o ka mea ma muli o ke kānāwai huinahāhāhā.

Hoʻopaʻa mau ʻia nā ʻano ʻano kino o kā lākou mea kumu. ʻO ka pahu i hana ʻia mai ka metala hiki ʻole ke puhi ʻia a hiki ke hana hou ʻia ma ke ʻano he kumu. Ua like kona coefficient o ka hoonui wela oiai e emi ana paha ka hookui wela.

ʻOiai ʻo ka nui o nā patents e wehewehe i nā ʻano topological hiki ke kūpono, nā mea constitutive, a me nā ʻano hana, ʻaʻole hiki ke manaʻo ʻia nā pahu metala he waiwai a he liʻiliʻi nā mea kūʻai aku i loaʻa i ka honua holoʻokoʻa.