Car and engine noises you shouldn’t ignore

What are some common car and engine noises I shouldn’t ignore? <svg xmlns="http://www.w3.org/2000/svg" fill="none" viewBox="0 0 24 25" class="_root_1u45k_1 _m_1u45k_16" aria-hidden="true" focusable="false">

Is brake squeal something to be concerned about? <svg xmlns="http://www.w3.org/2000/svg" fill="none" viewBox="0 0 24 25" class="_root_1u45k_1 _m_1u45k_16" aria-hidden="true" focusable="false">

Can rattling exhaust be dangerous? <svg xmlns="http://www.w3.org/2000/svg" fill="none" viewBox="0 0 24 25" class="_root_1u45k_1 _m_1u45k_16" aria-hidden="true" focusable="false">

What should I do if I hear metal-on-metal scraping? <svg xmlns="http://www.w3.org/2000/svg" fill="none" viewBox="0 0 24 25" class="_root_1u45k_1 _m_1u45k_16" aria-hidden="true" focusable="false">