The word metastasis is singular, metastases is plural.
Metastases
Metastases is the plural formation of the word mestasis.
Metastasis
Depends on the form. If cancer has spread, it is said to have metastasized. The spreading itself is called metastasis. "Lung carcinoma with metastasis to the liver."
The plural form of "do" is "do" and the plural form of "don't" is "don't." These words do not change in the plural form when used in a sentence.
The plural form of him, her, or it is them. (objective pronouns)
Bridges is the plural form of bridge.
malignant
The plural form of "was" is "were."
The plural form of "I" is "we."
The plural form of "is" is "are."