Teachers faced adversity in 2020 when the COVID-19 pandemic emerged. This qualitative instrumental case study sought to capture the lived experiences of K-5 teachers in the Guam Department of Education, who endured teaching in three modalities over a span of two years consecutively, between February 2020 to February 2022. The purpose was to explore teacher perceptions of teaching during the pandemic. The aim was to understand how teacher self-efficacy and teaching with enthusiasm relates to student engagement and subsequent learning, during the pandemic. Data collection occurred in two methods: (1) a questionnaire, and (2) focus group. A total of ten teachers responded to Teachers' Experiences Questionnaire and of the ten teachers, four self-selected to participate in the focus group interview. Data was aggregated and coded. From the questionnaire, four themes materialized: (1) models of learning, (2) teaching and pedagogy, (3) student psychology, and (4) student engagement. From the focus group, three themes were identified: (1) teacher-efficacy, (2) teacher behaviors, and (3) instructional strategies. The study found that the teachers' feelings and love for teaching as experienced enthusiasm, positively affected their teaching practice by showing displayed enthusiasm as an instructional behavior or teaching style. The extant literature was able to connect findings with the study, confirming that enthusiastic instructions obtain engagement. The study addressed a gap in literature by exploring teachers' experiences during a pandemic to inform practitioner guidelines for 'Enthused Instruction.' The current study added to the body of research on teacher self-efficacy, teaching with enthusiasm, and strategies to engage learners. Further recommendations of the study would entail special education, English language learner teachers, other language, and gifted and talented teachers. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com.bibliotheek.ehb.be/en-US/products/dissertations/individuals.shtml.]