Inclusion Criteria:

• Cohort 1:
• Capacity and willingness to participant in TMS, and fMRI as well as satisfying criteria for diagnosis.
• * Between 18 and 89 years of age.
• * Ability to obtain a Motor Threshold (MT) with single pulse TMS
• * Ability to safely and comfortably undergo an MRI and TMS
• * Able to read, verbalize, understand and voluntarily sign the Informed Consent Form prior to participating in any study-specific procedures or assessments
• * Depression (PHQ-9 \>= 10 and functional impairment present indicated with "difficulty" question OR sufficiently depressed to be enrolled in rTMS therapy)
• * Confirmed diagnosis of Major Depressive Disorder (MDD)
• * Can maintain all existing treatments (e.g. psychopharmacology, psychotherapy, etc.,) throughout course of the three sessions (psychological / functional assessments, MRI, and TMS), with modifications only as needed for clinical management
• * Is a Veteran
• Cohort 2:
• * Between 18 and 89 years of age
• * Ability to safely and comfortably undergo an MRI and tES
• * Ability to read, verbalize, understand, and voluntarily sign the Informed Consent Form prior to participating in any study-specific procedures or assessments
• * Depression (PHQ-9 \>= 10) and endorse that the COVID-19 pandemic has worsened their depression OR have a score on the COVID Stress Scale (CSS) on any item of 3 or greater indicating stressor is "very" or "often" a problem will allow the Veteran to enter the study

Exclusion Criteria:

• * Participants who can not safely and comfortably undergo MRI OR TMS (or TES for Cohort 2)
• * If their language is not primarily English they may be excluded depending on how dependent the imaging and cognitive tasks are on language
• * Additionally, participants may be excluded if they do not fully understand the consenting process and cannot communicate sufficiently in English to participate in the therapy (d/t language barrier, etc.)
• * An example of safety screen details for an MRI is detailed in the Stanford University MRI screening form
• * MRI exclusions include having any non-removable device or implant that makes scanning unsafe, claustrophobia, and size (e.g. weight, girth) beyond the constraints of the MRI and scanner bed
• * For TMS the investigators will follow safety guidelines set by Rossi et. al.,2009
• * Specifically, the investigators will not include subjects whose Motor Threshold (MT) is greater than 84% of maximum device output because mathematically they would not be able to be safely stimulated using the standard 120% of MT (i.e. the device cannot stimulate more than 100% of its potential output)
• * The investigators will report these high MT data in our secondary analyses. Additional TMS exclusions include any history or condition that puts patients at risk for a seizure
• * Pregnant or planning to become pregnant within the next 3 months
• * Lifetime history of moderate or severe traumatic brain injury, current unstable medical conditions, current (or past if appropriate) significant neurological disorder, or lifetime history of:
• * seizure disorder
• * primary or secondary CNS tumors
• * stroke
• * cerebral aneurysm
• * Significant cognitive impairment (Montreal Cognitive Assessment \[MoCA\] \< 16)
• * Comorbidities (e.g. PTSD) determined not to be the primary diagnosis
• * Have a lifetime diagnosis of schizophrenia, schizoaffective disorder, schizophreniform, delusional disorder, or current psychotic symptoms
• * Have a diagnosis of obsessive-compulsive disorder assessed by a study investigator to be causing greater impairment than MDD
• * Have active suicidal intent or plan in which case Dr. Rosen will determine whether the patient needs to be referred for hospitalization
• * Presence of any other condition or circumstance that, in opinion of the investigator team, has the potential to prevent study completion and/or to have a confounding effect on outcome assessments
• Exclusion Criteria for Cohort 2:
• * Participants who cannot safely and comfortably undergo MRI or TES
• * Pregnant or lactating female or planning to become pregnant within the next 3 months
• * Lifetime history of moderate or severe traumatic brain injury or tumor
• * Significant cognitive impairment (Montreal Cognitive Assessment \[MoCA\] \< 16 OR equivalent score on \[MoCA-BLIND\] and judgement of a clinician that the test is validly reflecting a significant disabling cognitive impairment
• * Have a lifetime diagnosis of:
• * schizophrenia
• * schizoaffective disorder
• * schizophreniform
• * delusional disorder
• * or current psychotic symptoms
• * Have a diagnosis of obsessive-compulsive disorder or unstable substance use disorder
• * Presence of actively infections/contagious disease such as the flu or SARS-CoV-2