Background Patients with metastatic lung cancer have a series of symptoms and many severe treatment-related side effects. However, little evidence is in support of benefits in performing exercise during their hospitalization. The purpose of this study was to understand exercise experiences inpatients with metastatic lung cancer. \n\nMethods A qualitative approach with face-to-face in-depth interview was conducted at an inpatient ward of a medical center in central Taiwan, on 24 recruited participants with metastatic lung cancer. The interview transcripts went through a narrative analysis by a group of qualitative research experts to extract and validate the main themes. \n\nResults Three primary themes were identified: (a) modifying exercise to maximize physical functions, (b) living with symptoms and frustration but continuing exercise, and (c) doing exercise to sustain hopes, inner power, and life. Two secondary findings were: (a) most participants adopted walking as their main form of exercise because of its flexibility, and (b)participants, according to the severity of their symptoms, adjusted their exercise towards shorter time durations and shorter distances, slower speeds, and higher frequencies. \n\nConclusions Participants with metastatic lung cancer adjusted their exercise behaviors to balance disease and treatment-induced deteriorations and to boost themselves to fight cancer and sustain survival. Individualized exercise schemes should be adopted in clinical practice to enhance their physical functions and life meaning. Such a home-based rehabilitation program in exercise was acceptable to most participants with metastatic lung cancer, including improvements in physical fitness, motivation, and the ability to manage symptoms.